a) $\frac{3}{5}$ x - $\frac{1}{4}$ = $\frac{5}{2}$
⇔ $\frac{3}{5}$ x = $\frac{5}{2}$ + $\frac{1}{4}$
⇔ $\frac{3}{5}$ x = $\frac{10}{4}$ + $\frac{1}{4}$
⇔ $\frac{3}{5}$ x = $\frac{11}{4}$
⇔ x = $\frac{11}{4}$ : $\frac{3}{5}$
⇔ x = $\frac{55}{12}$
Vậy x ∈ {$\frac{55}{12}$ }
b) $\frac{1}{2}$ x - $\frac{1}{3}$ x = $\frac{1}{6}$
⇔ x ( $\frac{1}{2}$ - $\frac{1}{3}$) = $\frac{1}{6}$
⇔ x ( $\frac{3}{6}$ - $\frac{2}{6}$) = $\frac{1}{6}$
⇔ x . $\frac{1}{6}$ = $\frac{1}{6}$
⇔ x = 1
Vậy x ∈ {1}
