Tìm x a) x + 2/3= 5/4;

a) \(x + \frac{2}{3} = \frac{5}{4}\)

\(x = \frac{5}{4} - \frac{2}{3}\)

\(x = \frac{7}{{12}}\).

Vậy \(x = \frac{7}{{12}}\).

b) \(\left( {x + \frac{3}{{10}}} \right).\frac{1}{2} = \frac{{17}}{{12}}\)

\(x + \frac{3}{{10}} = \frac{{17}}{{12}}:\frac{1}{2}\)

\(x + \frac{3}{{10}} = \frac{{17}}{6}\)

\(x = \frac{{17}}{6} - \frac{3}{{10}}\)

\(x = \frac{{76}}{{30}}\).

Vậy \(x = \frac{{76}}{{30}}\).