Đáp án:
a. x × $\frac{3}{4}$ + $\frac{2}{5}$ = $\frac{9}{20}$
x × $\frac{3}{4}$ = $\frac{9}{20}$ - $\frac{2}{5}$
x × $\frac{3}{4}$ = $\frac{1}{20}$
x = $\frac{1}{20}$ : $\frac{3}{4}$
x = $\frac{1}{15}$.
b. 0,25 + $\frac{1}{2}$ : x = 3,25
$\frac{1}{2}$ : x = 3,25 - 0,25
$\frac{1}{2}$ : x = 3
x = $\frac{1}{2}$ : 3
x = $\frac{1}{6}$.
c. x × $\frac{2}{3}$ + x = $\frac{5}{6}$
x × $\frac{2}{3}$ + x × 1 = $\frac{5}{6}$
x × ( $\frac{2}{3}$ + 1) = $\frac{5}{6}$
x × $\frac{5}{3}$ = $\frac{5}{6}$
x = $\frac{5}{6}$ : $\frac{5}{3}$
x = $\frac{1}{2}$.
#_Kaiz_
