4-(4 целых 21/40-5,25):1целую 7/20

Решим пример по действиям:

1) 4 21/40 = (4 * 40 + 21)/40 = 181/40;

2) 181/40 - 525/100 = 181/40 - 210/40 = (181 - 210)/40 = -29/40;

3) 1 7/20 = (1 * 20 + 7)/20 = 27/20;

4) -29/40 : 27/20 = - 29/40 * 20/27 = - (29 * 20)/(40 * 27) = -29/54;

5) 4 - (-29/54) = 4 + 29/54 = 216/54 + 29/54 = (216 + 29)/54 = 245/54;

Ответ: 245/54.