Tìm x biết: (a) 5/x − 1/6 = − 12/21 : 6/7 .

a) \(5x - \frac{1}{6} = \frac{{ - 12}}{{21}}:\frac{6}{7}\)

\(5x - \frac{1}{6} = \frac{{ - 2}}{3}\)

\(5x = \frac{{ - 2}}{3} + \frac{1}{6}\)

\(5x = \frac{{ - 1}}{2}\)

\(x = \frac{{ - 1}}{2}:5\)

\(x = \frac{{ - 1}}{{10}}\)

Vậy \(x = \frac{{ - 1}}{{10}}\).

b) \(\frac{{x + 1}}{{16}} = \frac{{ - 3}}{4}\)

\(\frac{{x + 1}}{{16}} = \frac{{ - 12}}{{16}}\)

\(x + 1 = - 12\)

\(x = - 13\)

Vậy \(x = - 13\).