Tìm x: a) x : 12,5 = 1,2 + 25% b) 0,4 x - 1/5 x = 3/4

* Hướng dẫn giải

a)

$\begin{array}{l}x.12,5=1,2+25\%\\ x.12,5=1,2+0,25\\ x.12,5=1,45\\ x=1,45:12,5\\ x=0,116\end{array}$

b)

$\begin{array}{l}0,4x-\frac{1}{5}x=\frac{3}{4}\\ \left(\frac{2}{5}-\frac{1}{5}\right)x=\frac{3}{4}\\ \frac{1}{5}x=\frac{3}{4}\\ x=\frac{15}{4}\end{array}$