\[\boxed{\mathbf{200\ (200).}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
Пояснение.
Решение.
\[1)\ \frac{a}{5} = \frac{6}{15}\]
\[\frac{a}{5} = \frac{2}{5} \Longrightarrow a = 2.\]
\[2)\ \frac{1}{12} = \frac{4}{a}\]
\[\frac{4}{48} = \frac{4}{a} \Longrightarrow a = 48.\]
\[3)\ \frac{56}{70} = \frac{8}{a}\]
\[\frac{8}{10} = \frac{8}{a} \Longrightarrow a = 10.\]
\[4)\ \frac{a}{60} = \frac{6}{5}\]
\[\frac{a}{60} = \frac{72}{60} \Longrightarrow a = 72.\]