Ответ:

\(\frac{2}{3}=\frac{8}{12}\), поэтому \(\frac{2}{3}+\frac{7}{12}=\frac{15}{12}=\frac54\).

\(\frac{16}{25}\cdot\frac54=\frac45\).

\(\frac{9}{10}:\frac{15}{16}=\frac{9}{10}\cdot\frac{16}{15}=\frac{24}{25}\).

\(\frac45-\frac{24}{25}=\frac{20}{25}-\frac{24}{25}=-\frac4{25}\).

Ответ: \(-\frac4{25}\).