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