a) -37,8 : 3,6 + 12,5 * (-0,6) = -10,5 - 7,5 = -18
б) $$5\frac{3}{7} - (2\frac{1}{2} + 1\frac{1}{3}) : \frac{1}{6} = \frac{38}{7} - (\frac{5}{2} + \frac{4}{3}) * 6 = \frac{38}{7} - (\frac{15+8}{6}) * 6 =$$
$$\frac{38}{7} - \frac{23}{6} * 6 = \frac{38}{7} - 23 = \frac{38 - 161}{7} = \frac{-123}{7} = -17\frac{4}{7}$$