Tìm giá trị của x , biết: (a) 3 x − 5/6 = − 14/21 : 2/7 . (b) x − 1/12 = − 5/4 .

a) \(3x - \frac{5}{6} = \frac{{ - 14}}{{21}}:\frac{2}{7}\)

\(3x - \frac{5}{6} = \frac{{ - 2}}{3}.\frac{7}{2}\)

\(3x - \frac{5}{6} = \frac{{ - 7}}{3}\)

\(3x = \frac{{ - 7}}{3} + \frac{5}{6}\)

\(3x = \frac{{ - 14}}{6} + \frac{5}{6}\)

\(3x = \frac{{ - 3}}{2}\)

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

Vậy \(x = \frac{{ - 1}}{2}\).

b) \(\frac{{x - 1}}{{12}} = \frac{{ - 5}}{4}\)

\(\frac{{x - 1}}{{12}} = \frac{{ - 15}}{{12}}\)

\(x - 1 = - 15\)

\(x = - 15 + 1\)

\(x = - 14\)

Vậy \(x = - 14\).