5.14 Найдите значение суммы: a) -6+4/6+5/6; б) 2+5/9 -3 11/15;

а) $$ -6 \frac{2}{6} + 4 \frac{5}{6} = -6 \frac{2}{6} + 4 + \frac{5}{6} = -2 \frac{2}{6} + \frac{5}{6} = -2 + \frac{3}{6} = -1 \frac{3}{6} = -1 \frac{1}{2}$$

б) $$2 \frac{4}{9} - 3 \frac{11}{20} = \frac{22}{9} - \frac{71}{20} = \frac{22 \cdot 20}{9 \cdot 20} - \frac{71 \cdot 9}{20 \cdot 9} = \frac{440}{180} - \frac{639}{180} = - \frac{199}{180} = -1 \frac{19}{180}$$

Ответ: а) $$-1 \frac{1}{2}$$, б) $$-1 \frac{19}{180}$$