Задание 4. Найдите значение выражения 1) $$\frac{1}{\frac{1}{28}+\frac{1}{12}}$$; 2) $$\frac{1}{\frac{1}{14}-\frac{1}{63}}$$

1) $$\frac{1}{\frac{1}{28}+\frac{1}{12}} = \frac{1}{\frac{3}{84}+\frac{7}{84}} = \frac{1}{\frac{10}{84}} = \frac{84}{10} = 8,4$$. 2) $$\frac{1}{\frac{1}{14}-\frac{1}{63}} = \frac{1}{\frac{9}{126}-\frac{2}{126}} = \frac{1}{\frac{7}{126}} = \frac{126}{7} = 18$$.