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

39) $$\frac{8}{15} (\frac{3}{4}x - \frac{5}{16}y) - \frac{2}{3} (\frac{6}{20}x - \frac{4}{3}y) =$$ $$ \frac{8 \cdot 3}{15 \cdot 4}x - \frac{8 \cdot 5}{15 \cdot 16}y - \frac{2 \cdot 6}{3 \cdot 20}x + \frac{2 \cdot 4}{3 \cdot 3}y =$$ $$ \frac{24}{60}x - \frac{40}{240}y - \frac{12}{60}x + \frac{8}{9}y =$$ $$ \frac{2}{5}x - \frac{1}{6}y - \frac{1}{5}x + \frac{8}{9}y =$$ $$ \frac{2}{5}x - \frac{1}{5}x - \frac{1}{6}y + \frac{8}{9}y =$$ $$ \frac{1}{5}x + (-\frac{1 \cdot 3}{6 \cdot 3} + \frac{8 \cdot 2}{9 \cdot 2})y =$$ $$ \frac{1}{5}x + (-\frac{3}{18} + \frac{16}{18})y =$$ $$ \frac{1}{5}x + \frac{13}{18}y$$

Ответ: $$\frac{1}{5}x + \frac{13}{18}y$$