Решие пример с дробями по действиям:
(3 1/5*1 1/24+3*5/6)*4/21-1 1/9
3 1/5 * 1 1/24 = 16/5 * 25/24 = (16*25)/(5*24)=400/120=10/3
3*5/6=15/6
10/3+15/6=20/6+15/6=(20+15)/6=35/6
35/6 * 4/21= (35*4)/(6*21)=140/126 = 70/63
70/63 - 1 1/9= 70/63 - 10/9 = 70/63 - 70/63 = 0