4. Решите уравнения: a) x - 5 3/8 = 7 1/8; б) 6/7 * x = 4 3/7; в) 7/12 : x = 2/3

a) \( x - 5 \frac{3}{8} = 7 \frac{1}{8} \) \( x = 7 \frac{1}{8} + 5 \frac{3}{8} \) \( x = 12 \frac{4}{8} \) \( x = 12 \frac{1}{2} \) б) \( \frac{6}{7} \cdot x = 4 \frac{3}{7} \) \( \frac{6}{7} \cdot x = \frac{31}{7} \) \( x = \frac{31}{7} : \frac{6}{7} \) \( x = \frac{31}{7} \cdot \frac{7}{6} \) \( x = \frac{31}{6} \) \( x = 5 \frac{1}{6} \) в) \( \frac{7}{12} : x = \frac{2}{3} \) \( x = \frac{7}{12} : \frac{2}{3} \) \( x = \frac{7}{12} \cdot \frac{3}{2} \) \( x = \frac{7}{4} \cdot \frac{1}{2} \) \( x = \frac{7}{8} \)