11-6 13/21-3/14 по действиям
1. 11-6 целых и 13/21 = (11*21-(6*21+13)) / 21 = (231-126-13)/21 = 92/21 2. 92/21-3/14 = (92*2-3*3)/42 = (184-9)/14 = 175/42 = 4 целых и 1/6