19) 8/15(3- 3/4 x – 5/16 y) – 3/20(6 – 2/3 x – 4/9 y) =

19) $$\frac{8}{15}(3- \frac{3}{4} x – \frac{5}{16} y) – \frac{3}{20}(6 – \frac{2}{3} x – \frac{4}{9} y) = \frac{24}{15} - \frac{24}{60}x - \frac{40}{240}y - \frac{18}{20} + \frac{6}{60}x + \frac{12}{180}y = \frac{8}{5} - \frac{2}{5}x - \frac{1}{6}y - \frac{9}{10} + \frac{1}{10}x + \frac{1}{15}y = \frac{16}{10} - \frac{9}{10} - \frac{4}{10}x + \frac{1}{10}x - \frac{5}{30}y + \frac{2}{30}y = \frac{7}{10} - \frac{3}{10}x - \frac{3}{30}y = \frac{7}{10} - \frac{3}{10}x - \frac{1}{10}y$$

Ответ: $$\frac{7}{10} - \frac{3}{10}x - \frac{1}{10}y$$