№ 1 1 1 — + —— 30 42 ———— 1 — 7

Решим пример №1 из Блока №2:

$$ \frac{\frac{1}{30} + \frac{1}{42}}{\frac{1}{7}} = \frac{\frac{1 \cdot 7}{30 \cdot 7} + \frac{1 \cdot 5}{42 \cdot 5}}{\frac{1}{7}} = \frac{\frac{7}{210} + \frac{5}{210}}{\frac{1}{7}} = \frac{\frac{7+5}{210}}{\frac{1}{7}} = \frac{\frac{12}{210}}{\frac{1}{7}} = \frac{12}{210} : \frac{1}{7} = \frac{12}{210} \cdot \frac{7}{1} = \frac{12 \cdot 7}{210 \cdot 1} = \frac{12}{30} = \frac{2}{5} $$

Ответ: $$\frac{2}{5}$$