a) Сравним дроби $$\frac{38}{57}$$ и $$\frac{8}{12}$$:
$$ \frac{38}{57} = \frac{2 \cdot 19}{3 \cdot 19} = \frac{2}{3} $$
$$ \frac{8}{12} = \frac{2 \cdot 4}{3 \cdot 4} = \frac{2}{3} $$
Таким образом, $$\frac{38}{57} = \frac{8}{12} = \frac{2}{3}$$
Ответ: $$\frac{38}{57} = \frac{8}{12}$$