8. (3/5 m³n²) - (1/4 n²m + 5/8 n³m - 7/10 m³n²)

8. (\frac{3}{5}m^3n^2) - (\frac{1}{4}n^2m + \frac{5}{8}n^3m - \frac{7}{10}m^3n^2) = \frac{3}{5}m^3n^2 - \frac{1}{4}n^2m - \frac{5}{8}n^3m + \frac{7}{10}m^3n^2 = (\frac{3}{5}m^3n^2 + \frac{7}{10}m^3n^2) - \frac{1}{4}n^2m - \frac{5}{8}n^3m = (\frac{6}{10}m^3n^2 + \frac{7}{10}m^3n^2) - \frac{1}{4}n^2m - \frac{5}{8}n^3m = \frac{13}{10}m^3n^2 - \frac{1}{4}n^2m - \frac{5}{8}n^3m

Ответ: \frac{13}{10}m^3n^2 - \frac{1}{4}n^2m - \frac{5}{8}n^3m