Tìm x a) 2/9 - 7/8 x = 1/3 b) 4/5 + 5/7 : x = 1/6

* Hướng dẫn giải

a) 

$\begin{array}{l}\frac{2}{9}-\frac{7}{8}.x=\frac{1}{3}\\ \frac{7}{8}.x=\frac{2}{9}-\frac{1}{3}\\ \frac{7}{8}.x=\frac{-1}{3}\\ x=\frac{-1}{3}:\frac{7}{8}\\ x=\frac{-8}{21}\end{array}$

b)

$\begin{array}{l}\frac{4}{5}+\frac{5}{7}:x=\frac{1}{6}\\ \frac{5}{7}:x=\frac{1}{6}-\frac{4}{5}\\ \frac{5}{7}:x=\frac{-19}{30}\\ x=\frac{5}{7}:\frac{-19}{30}\\ x=\frac{-150}{133}\end{array}$