10) -2 3/5+(-7 3/10);

10) $$-2 \frac{3}{5} + (-7 \frac{3}{10}) = -2 \frac{3}{5} - 7 \frac{3}{10} = -\frac{13}{5} - \frac{73}{10} = -\frac{13 \cdot 2}{5 \cdot 2} - \frac{73}{10} = -\frac{26}{10} - \frac{73}{10} = \frac{-26 - 73}{10} = -\frac{99}{10} = -9 \frac{9}{10}$$

Ответ: $$-9 \frac{9}{10}$$