Tìm x, biết: a) 3/4 + 2/5x = 29/60 b) 4/5x - 1/2* 3/2 = -9/2

* Hướng dẫn giải

a) $\frac{3}{4}+\frac{2}{5}x=\frac{29}{60}$ 

$\frac{2}{5}x=\frac{29}{60}-\frac{3}{4}$ 

$\frac{2}{5}x=\frac{29}{60}-\frac{45}{60}$ 

$\frac{2}{5}x=\frac{-16}{60}$ 

$x=\frac{-16}{60}:\frac{2}{5}$ 

$x=\frac{-16}{60}.\frac{5}{2}$ 

$x=\frac{\mathrm{2.4.}(-2).5}{\mathrm{5.3.4.2}}$ 

$x=\frac{-2}{3}$ 

b) $\frac{4}{5}x-\frac{1}{2}.\frac{3}{2}=\frac{-9}{2}$ 

$\frac{4}{5}x-\frac{3}{4}=\frac{-9}{2}$ 

$\frac{4}{5}x=\frac{-9}{2}+\frac{3}{4}$ 

$\frac{4}{5}x=\frac{(-9).2}{4}+\frac{3}{4}$ 

$\frac{4}{5}x=\frac{-18}{4}+\frac{3}{4}$ 

$\frac{4}{5}x=\frac{-15}{4}$ 

$x=\frac{-15}{4}:\frac{4}{5}$ 

$x=\frac{-15}{4}.\frac{5}{4}$ 

$x=\frac{-75}{16}$