0,9(0,4-1 2/3м)-0,2(0,8-7 1/2м)= Упростите выражение

Решите задачу:

$0,9(0,4-1 \frac{2}{3}m)-0,2(0,8-7 \frac{1}{2}m)=[tex]\frac{9}{10} ( \frac{4}{10} -\frac{5}{3}m)- \frac{2}{10} ( \frac{8}{10} -\frac{15}{2}m)$ $= \frac{9}{10} ( \frac{2}{5} -\frac{5}{3}m)- \frac{1}{5} ( \frac{4}{5} -\frac{15}{2}m)=$ $\frac{9}{10}* \frac{2}{5} - \frac{9}{10}*\frac{5}{3}m- \frac{1}{5}* \frac{4}{5} +\frac{1}{5}*\frac{15}{2}m= \frac{9*1}{5*5} - \frac{3*1}{2*1} m- \frac{1*4}{5*5}+ \frac{1*3}{1*2}m=$ $\frac{9}{25} - \frac{3}{2} m- \frac{4}{25}+ \frac{3}{2}m= \frac{9-4}{25}= \frac{5}{25} = \frac{1}{5}$