(a) Thực hiện phép tính: 5/8 ⋅ 23/7 − 5/8 ⋅ 9/7 + 3/4 . (b) Tìm x , biết: − 5 x − 2/3 = 8/3 .

a) \(\frac{5}{8} \cdot \frac{{23}}{7} - \frac{5}{8} \cdot \frac{9}{7} + \frac{3}{4}\)

\( = \frac{5}{8} \cdot \left( {\frac{{23}}{7} - \frac{9}{7}} \right) + \frac{3}{4}\)

\( = \frac{5}{8} \cdot \frac{{14}}{7} + \frac{3}{4}\)

\( = \frac{5}{8} \cdot 2 + \frac{3}{4}\)

\( = \frac{5}{4} + \frac{3}{4} = \frac{8}{4} = 2\).

b) \( - 5x - \frac{2}{3} = \frac{8}{3}\)

\( - 5x = \frac{8}{3} + \frac{2}{3}\)

\( - 5x = \frac{{10}}{3}\)

\(x = \frac{{10}}{3}:\left( { - 5} \right)\)

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

Vậy \(x = \frac{{ - 2}}{3}.\)