Đáp án:
a, $\frac{-2}{15}$ - x = $\frac{-3}{10}$
⇔ x = $\frac{-2}{15}$ - $\frac{-3}{10}$
⇔ x = $\frac{-2}{15}$ + $\frac{3}{10}$
⇔ x = $\frac{1}{6}$
b, x + $\frac{1}{3}$ = $\frac{2}{5}$ - ( -$\frac{1}{3}$)
⇔ x + $\frac{1}{3}$ = $\frac{2}{5}$ + $\frac{1}{3}$
⇔ x + $\frac{1}{3}$ = $\frac{6}{15}$ + $\frac{5}{15}$ =$\frac{11}{15}$
⇔ x = $\frac{11}{15}$ - $\frac{1}{3}$
⇔ x = $\frac{2}{5}$
c, $\frac{3}{7}$ - x = $\frac{1}{4}$ - ( - $\frac{3}{5}$ )
⇔ $\frac{3}{7}$ - x = $\frac{1}{4}$ + $\frac{3}{5}$
⇔ $\frac{3}{7}$ - x = $\frac{17}{20}$
⇔ x = $\frac{3}{7}$ - $\frac{17}{20}$
⇔ x = $\frac{-59}{140}$
