Đáp án:
Giải thích các bước giải:
x + $\frac{2}{5}$ : $\frac{3}{4}$ = $\frac{1}{4}$
x + $\frac{2}{5}$ × $\frac{4}{3}$ - $\frac{1}{4}$ = 0
x + $\frac{8}{15}$ - $\frac{1}{4}$ = 0
x = $\frac{15}{60}$ - $\frac{32}{60}$
x = $\frac{-17}{60}$
b) $\frac{2}{7}$ : (11 - x) + $\frac{2}{3}$ = $\frac{1}{2}$
⇔ $\frac{2}{7}$ : (11 - x) = $\frac{1}{2}$ - $\frac{2}{3}$
⇔ $\frac{2}{7}$ : (11 - x) = $\frac{3}{6}$ - $\frac{4}{6}$
⇔ $\frac{2}{7}$ : (11 - x) = $\frac{-1}{6}$
⇔ 11 - x = $\frac{2}{7}$ : $\frac{-1}{6}$
⇔ 11 - x = $\frac{2}{7}$ . (-6)
⇔ 11 -x = $\frac{-12}{7}$
⇔ x = 11 - $\frac{-12}{7}$\
⇔ x = $\frac{77}{7}$ + $\frac{12}{7}$
⇔ x = $\frac{89}{7}$
