Tìm x, biết: a) -2/3 : x + 5/8 = -7/12 b) 1/2 x + 2 1/2 = 3 1/2 x - 3/4

* Hướng dẫn giải

$\begin{array}{l}a)-\frac{2}{3}:x+\frac{5}{8}=-\frac{7}{12}\\ \frac{-2}{3}:x=-\frac{7}{12}-\frac{5}{8}\\ \frac{-2}{3}:x=-\frac{29}{24}\\ x=\frac{16}{29}\end{array}$

$\begin{array}{l}b)\frac{1}{2}x+2\frac{1}{2}=3\frac{1}{2}x-\frac{3}{4}\\ \left(\frac{1}{2}-3\frac{1}{2}\right)x=-\frac{3}{4}-\frac{5}{4}\\ -3x=-2\\ x=\frac{2}{3}\end{array}$