Bỏ ngoặc rồi thực hiện phép tính: ( − 15/7 − 13/9 ) − ( − 7/9 − 15/7 + 2/3 ) .

\[\left( {\frac{{ - 15}}{7} - \frac{{13}}{9}} \right) - \left( {\frac{{ - 7}}{9} - \frac{{15}}{7} + \frac{2}{3}} \right)\]

\( = \frac{{ - 15}}{7} - \frac{{13}}{9} + \frac{7}{9} + \frac{{15}}{7} - \frac{2}{3}\)

\( = \left( {\frac{{ - 15}}{7} + \frac{{15}}{7}} \right) + \left( { - \frac{{13}}{9} + \frac{7}{9}} \right) - \frac{2}{3}\)

\( = 0 + \frac{{ - 6}}{9} - \frac{2}{3}\)

\( = \frac{{ - 2}}{3} - \frac{2}{3} = \frac{{ - 4}}{3}.\)