a) (9/16 + 1/4) - 1/16;
$$\frac{9}{16} + \frac{1}{4} - \frac{1}{16} = \frac{9}{16} - \frac{1}{16} + \frac{1}{4} = \frac{9-1}{16} + \frac{1}{4} = \frac{8}{16} + \frac{1}{4} = \frac{1}{2} + \frac{1}{4} = \frac{1 \cdot 2}{2 \cdot 2} + \frac{1}{4} = \frac{2}{4} + \frac{1}{4} = \frac{2+1}{4} = \frac{3}{4}$$
Ответ: 3/4