\(12+\frac{x}{42}=\frac{5}{6}\)
\(\frac{x}{42}=\frac{5}{6}-12=\frac{5}{6}-\frac{72}{6}=-\frac{67}{6}=-\frac{469}{42}\)
=> x = -469
\(25-\frac{x}{40}=\frac{3}{8}\)
\(\frac{x}{40}=25-\frac{3}{8}=\frac{200}{8}-\frac{3}{8}=\frac{197}{8}=\frac{985}{40}\)
=> x = 985