19) \frac{8}{15}(\frac{3}{4}x-\frac{5}{16}y)-\frac{3}{20}(6\frac{2}{3}x-4\frac{4}{9}y) =

\frac{8}{15}(\frac{3}{4}x - \frac{5}{16}y) - \frac{3}{20}(6\frac{2}{3}x - 4\frac{4}{9}y) = \frac{8}{15}(\frac{3}{4}x - \frac{5}{16}y) - \frac{3}{20}(\frac{20}{3}x - \frac{40}{9}y) = \frac{2}{5}x - \frac{1}{6}y - x + \frac{2}{3}y = -\frac{3}{5}x + \frac{1}{2}y Ответ: -\frac{3}{5}x + \frac{1}{2}y