в) \frac{3}{4} : (1 - \frac{1}{4} + \frac{3}{8});

1) 1 - \frac{1}{4} = \frac{4}{4} - \frac{1}{4} = \frac{3}{4}

2) \frac{3}{4} + \frac{3}{8} = \frac{3 \cdot 2}{4 \cdot 2} + \frac{3}{8} = \frac{6}{8} + \frac{3}{8} = \frac{9}{8}

3) \frac{3}{4} : \frac{9}{8} = \frac{3}{4} \cdot \frac{8}{9} = \frac{3 \cdot 8}{4 \cdot 9} = \frac{24}{36} = \frac{2}{3}

Ответ: \frac{2}{3}