Đáp án:
Giải thích các bước giải:
($\frac{1}{4}$ -$\frac{3}{10}$ .x).$\frac{1}{3}$ -$\frac{1}{4}$ =$\frac{-31}{6}$
($\frac{1}{4}$ -$\frac{3}{10}$ . x) .$\frac{1}{3}$ =$\frac{-31}{6}$ + $\frac{1}{4}$
($\frac{1}{4}$ -$\frac{3}{10}$ . x) .$\frac{1}{3}$=$\frac{-59}{12}$
$\frac{1}{4}$ -$\frac{3}{10}$ . x=$\frac{-59}{12}$ : $\frac{1}{3}$
$\frac{1}{4}$ -$\frac{3}{10}$ . x=$\frac{-59}{4}$
$\frac{3}{10}$ . x=$\frac{1}{4}$ -$\frac{-59}{4}$
$\frac{3}{10}$ . x=15
x=15:$\frac{3}{10}$=50
c)x-25%.x=1/2
x-1/4.x=1/2
x.(1-1/4)=1/2
x.3/4=1/2
x = 1/2 : 3/4
x = 2/3
