Tìm x a) x - 4/5 = -3/4 b) -4/9 : x = 2,5 c) 1/7 : (3,5 - 2x) = 2 3/7

* Hướng dẫn giải

$\begin{array}{l}a)x=\frac{-3}{4}+\frac{4}{5}\iff x=\frac{1}{20}\\ b)x=\frac{-4}{9}:2,5\iff x=\frac{-8}{45}\\ c)3,5-2x=\frac{1}{7}:2\frac{3}{7}\iff 3,5-2x=\frac{1}{17}\\ \iff 2x=3,5-\frac{1}{17}\iff 2x=\frac{117}{34}\\ \iff x=\frac{117}{34}:2=\frac{117}{68}\end{array}$