21 целых 2/59 - 2/5 * (3 целых 15/28 : 9/28-1 целая: 1 целых 10/49) : 2=19

21 2/59-2/5 * (3 15/28 : 9/28 - 1: 1 10/49) : 2=19

1) 3 15/28 : 9/28 = 99/28 * 28/9 = 11

2) 1: 1 10/49 = 1 : 59/49 = 49/59

3) 11-49/59 = 10 10/59

4) 2/5 * 10 10/59 = 2/5 * 600/59 = 2*120/59 = 240/59

5) 240/59 : 2 = 120/59 = 2 2/59

6) 21 2/59 - 2 2/59 = 19