a)\(\left(\right. \frac{1}{2} + 1 , 5 \left.\right) \cdot x = \frac{1}{5}\)

\(2 \cdot x = \frac{1}{5}\)

\(x = \frac{1}{5} : 2\)

\(x=\frac{1}{10}\)
b) \(\left(\right. - 1 \frac{3}{5} + x \left.\right) : \frac{12}{13} = 2 \frac{1}{6}\)

\(- 1 \frac{3}{5} + x = \frac{13}{6} \cdot \frac{12}{13}\)
\(x = 2 + 1 \frac{3}{5}\)

\(x=3\frac{3}{5}\)
c) \(\left(\right. x : 2 \frac{1}{3} \left.\right) \cdot \frac{1}{7} = \frac{- 3}{8}\)

\(x \cdot \frac{3}{7} \cdot \frac{1}{7} = \frac{- 3}{8}\)

\(x = \frac{- 3}{8} : \frac{3}{49}\)
\(x = \frac{- 49}{8} = - 6 \frac{1}{8}\)
d) \(\frac{- 4}{7} \cdot x + \frac{7}{5} = \frac{1}{8} : \left(\right. - 1 \frac{2}{3} \left.\right)\)

\(\frac{- 4}{7} x + \frac{7}{5} = \frac{1}{8} \cdot \frac{- 3}{5}\)
\(- \frac{4}{7} x = \frac{- 3}{40} - \frac{7}{5} x = \frac{- 59}{40} : \frac{- 4}{7} = \frac{413}{160} = 2 \frac{93}{160}\)

a) \(x + \frac{1}{3} = \frac{1}{2} - \frac{5}{6}\)

\(x = - \frac{1}{3} - \frac{1}{3}\)

\(x = - \frac{2}{3}\);
b) \(\frac{3}{8} + \frac{5}{8} - \frac{1}{5} - x = \frac{1}{5}\)

\(x = 1 - \frac{1}{5} - \frac{1}{5}\)

\(x = \frac{3}{5}\).

a) \(x = 7 - \frac{2}{5} + 1 , 62 = 8 , 22\)
b) \(x = 4 \frac{3}{5} + \frac{1}{5} - \frac{1}{2} = 4 \frac{3}{10}\)
c) \(2 x - x = \frac{3}{5} + \frac{4}{7}\)
\(x = \frac{41}{35}\)
d) \(x = 3 \frac{1}{2} - \frac{5}{7} + \frac{1}{13} - 0.25\)
\(x = 2 \frac{223}{364}\)

a) \(A = \left[\right. \frac{2}{7} \left(\right. \frac{1}{4} - \frac{1}{3} \left.\right) \left]\right. : \left[\right. \frac{2}{7} \left(\right. \frac{1}{3} - \frac{2}{5} \left.\right) \left]\right. = \left(\right. \frac{1}{4} - \frac{1}{3} \left.\right) : \left(\right. \frac{1}{3} - \frac{2}{5} \left.\right) = 1 \frac{1}{4}\).
b) \(B = \frac{\frac{3}{4} \left(\right. \frac{1}{5} - \frac{2}{7} - \frac{1}{3} + \frac{2}{7} \left.\right)}{\frac{1}{5} \left(\right. \frac{2}{7} + \frac{1}{3} \left.\right) - \frac{1}{3} \left(\right. \frac{2}{7} + \frac{1}{3} \left.\right)} = \frac{\frac{3}{4} \left(\right. \frac{1}{5} - \frac{1}{3} \left.\right)}{\left(\right. \frac{1}{5} - \frac{1}{3} \left.\right) \left(\right. \frac{2}{7} + \frac{1}{3} \left.\right)} = 1 \frac{11}{52}\).

a) \(A=\frac{3}{5}.\frac{6}{7}+\frac{3}{7}.\frac{3}{5}-\frac{2}{7}.\frac{3}{5}\)
\(= \frac{3}{5} \cdot \left(\right. \frac{6}{7} + \frac{3}{7} - \frac{2}{7} \left.\right) = \frac{3}{5}\)
b) \(B=\left(\right.-13\cdot\frac{2}{5}+\frac{- 2}{9}\cdot\frac{2}{5}+\frac{2}{5}\cdot\frac{11}{9}\left.\right)\cdot\frac{5}{2}\)
\(= \left(\right. - 13 - \frac{2}{9} + \frac{11}{9} \left.\right) \cdot \frac{2}{5} \cdot \frac{5}{2} = - 13 + \left(\right. \frac{11}{9} - \frac{2}{9} \left.\right) = - 12.\)
c) \(C = \left(\right. \frac{- 4}{5} + \frac{5}{7} \left.\right) \cdot \frac{3}{2} + \left(\right. \frac{- 1}{5} + \frac{2}{7} \left.\right) \cdot \frac{3}{2} = \left(\right. \frac{- 4}{5} + \frac{5}{7} + \frac{- 1}{5} + \frac{2}{7} \left.\right) \cdot \frac{3}{2} = \left(\right. \left(\right. \frac{- 4}{5} + \frac{- 1}{5} \left.\right) + \left(\right. \frac{5}{7} + \frac{2}{7} \left.\right) \left.\right) \cdot \frac{3}{2} = 0.\)
d) \(D = \frac{4}{9} : \left(\right. \frac{1}{15} - \frac{10}{15} \left.\right) + \frac{4}{9} : \left(\right. \frac{2}{22} - \frac{5}{22} \left.\right)\)
\(=\frac{4}{9}:\frac{- 3}{5}+\frac{4}{9}:\frac{- 3}{22}=\frac{4}{9}\cdot\frac{- 5}{3}+\frac{4}{9}.\frac{- 22}{3}\)
\(=\frac{4}{9}\cdot\left(\right.\frac{- 5}{3}+\frac{- 22}{3}\left.\right)=\frac{4}{9}.\frac{- 27}{3}=-4.\)

a) \(P = \frac{2}{3} + \frac{1}{4} + \frac{3}{5} - \frac{7}{45} + \frac{5}{9} + \frac{1}{12} + \frac{1}{35}\) \(= \left(\right. \frac{2}{3} + \frac{1}{4} + \frac{1}{12} \left.\right) + \left(\right. \frac{5}{9} - \frac{7}{45} \left.\right) + \frac{3}{5} + \frac{1}{35} = 1 + \frac{4}{5} + \frac{3}{5} + \frac{1}{35} = 2 \frac{1}{35}\).
b) \(Q = \left(\right. 5 - 6 - 2 \left.\right) + \left(\right. - \frac{3}{4} - \frac{7}{4} + \frac{5}{4} \left.\right) + \left(\right. \frac{1}{5} + \frac{8}{5} - \frac{16}{5} \left.\right) = - \left(\right. 3 + \frac{5}{4} + \frac{7}{5} \left.\right)\) \(=-\frac{113}{20}\).

a) \(A = \left(\right. \frac{1}{3} + \frac{2}{3} \left.\right) - \left(\right. \frac{8}{15} + \frac{7}{15} \left.\right) + \left(\right. \frac{- 1}{7} + 1 \frac{1}{7} \left.\right) = 1 - 1 + 1 = 1\);
b) \(B = \left(\right. 0.25 - 1 \frac{1}{4} \left.\right) + \left(\right. \frac{3}{5} + \frac{2}{5} \left.\right) - \frac{1}{8}\)
\(= \left(\right. \frac{1}{4} - 1 - \frac{1}{4} \left.\right) + 1 - \frac{1}{8} = \frac{- 1}{8}\).

Dọc theo chiều dài, ta trồng được:

\(5.5 : \frac{1}{4} = 22\) (khóm hoa)

Dọc theo chiều rộng, ta trồng được:

\(3 , 75 : \frac{1}{4} = 15\) (khóm hoa)

Như vậy, số khóm hoa trồng được dọc theo hai cạnh của mảnh vườn là:

\(\left[\right. \left(\right. 22 + 15 \left.\right) . 2 \left]\right. - 4 = 70\) (khóm hoa)

Đáp số: 70 khóm hoa

a) \(\frac{1}{5}+\frac{4}{5}:x=0,75\)

\(\frac{1}{5}+\frac{4}{5}:x=\frac{3}{4}\)

\(\frac{4}{5} : x = \frac{3}{4} - \frac{1}{5}\)

\(\frac{4}{5} : x = \frac{11}{20}\)

\(x = \frac{16}{11}\);

b) \(x + \frac{1}{2} = 1 - x\)

 \(2 x = 1 - \frac{1}{2}\)

 \(2 x = \frac{1}{2}\)

 \(x = \frac{1}{4}\).

a) \(\frac{2}{3} \cdot \frac{5}{4} - \frac{3}{4} \cdot \frac{2}{3} = \frac{2}{3} \cdot \left(\right. \frac{5}{4} - \frac{3}{4} \left.\right) = \frac{2}{3} \cdot \frac{1}{2} = \frac{1}{3}\);
b) \(2 \cdot \left(\left(\right. \frac{- 3}{2} \left.\right)\right)^{2} - \frac{7}{2} = 2 \cdot \frac{9}{4} - \frac{7}{2} = \frac{9}{2} - \frac{7}{2} = 1\);
c) \(- \frac{3}{4} \cdot 5 \frac{3}{13} - 0 , 75 \cdot \frac{36}{13} = - \frac{3}{4} \cdot 5 \frac{3}{13} - \frac{3}{4} \cdot \frac{36}{13}\)
\(= - \frac{3}{4} \left(\right. 5 \frac{3}{13} + \frac{36}{13} \left.\right)\)
\(= - \frac{3}{4} \cdot 8 = - 6\).