а) \(\frac{x}{15}=\frac{1}{5}\)
\(x = \frac{15 \cdot 1}{5}\)
\(x = 3\)
б) \(\frac{10}{6}=\frac{5}{x}\)
\(x = \frac{6 \cdot 5}{10}\)
\(x = 3\)
в) \(\frac{8}{x}=\frac{2}{4}\)
\(x = \frac{8 \cdot 4}{2}\)
\(x = 16\)
г) \(\frac{18}{27}=\frac{x}{3}\)
\(x = \frac{18 \cdot 3}{27}\)
\(x = 2\)
Ответ: а) 3; б) 3; в) 16; г) 2.