Tìm x: a) x + 1/3 =5/12;

a) \[x + \frac{1}{3} = \frac{5}{{12}}\]

\[x = \frac{5}{{12}} - \frac{1}{3}\]

\[x = \frac{5}{{12}} - \frac{4}{{12}}\]

\[x = \frac{1}{{12}}\]

Vậy \[x = \frac{1}{{12}}\].

b) \(\frac{2}{3}x + \frac{1}{2}x = \frac{{15}}{{12}}\)

\(\left( {\frac{2}{3} + \frac{1}{2}} \right)\,\,.\,\,x = \frac{{15}}{{12}}\)

\(\frac{7}{6}x = \frac{{15}}{{12}}\)

\(x = \frac{{15}}{{12}}:\frac{7}{6}\)

\(x = \frac{{15}}{{14}}\).

Vậy \(x = \frac{{15}}{{14}}\).