б) в при S = 19 и а = 9/1.

б) $$S = a \cdot b$$

$$b = \frac{S}{a}$$

$$a = 9\frac{1}{2} = \frac{9 \cdot 2 + 1}{2} = \frac{19}{2}$$

$$S = 19$$

$$b = \frac{19}{\frac{19}{2}} = 19 \cdot \frac{2}{19} = 2$$

Ответ: 2