287. Упростите:

a) $$(-1,2a + 2,5b)4 - 3(3,2a – 0,6b) = -4,8a + 10b - 9,6a + 1,8b = -14,4a + 11,8b$$.
б) $$\frac{2}{3}(1,8 - 1\frac{1}{4}a) - 2\frac{1}{3}(1,2 - \frac{5}{14}a) = \frac{2}{3}(\frac{9}{5} - \frac{5}{4}a) - \frac{7}{3}(\frac{6}{5} - \frac{5}{14}a) = \frac{6}{5} - \frac{10}{12}a - \frac{14}{5} + \frac{35}{42}a = \frac{6}{5} - \frac{5}{6}a - \frac{14}{5} + \frac{5}{6}a = \frac{6-14}{5} = -\frac{8}{5}$$.