Выполните действие: 8/9 - 7/12; 11/50-3/25+1/20

Решите задачу:

$\frac{8}{9} - \frac{7}{12} = \frac{8*4}{9*4} - \frac{7*3}{12*3} = \frac{32}{36} - \frac{21}{36} = \frac{11}{36} \\ \\ \frac{11}{50} - \frac{3}{25} + \frac{1}{20} = \frac{11*2}{50*2} - \frac{3*4}{25*4} + \frac{1*5}{20*5} = \frac{22}{100}- \frac{12}{100} + \frac{5}{100} = \\ = \frac{12-2+5}{100} = \frac{15}{100} = \frac{3}{20}$