(5-1 ціла 1/3 ×1цілу 1/6)×21/31

(5 - 1 1/3 · 1 1/6) · 21/31 = 2 1/3

1) 1 1/3 · 1 1/6 = 4/3 · 7/6 = (2·7)/(3·3) = 14/9 = 1 5/9

2) 5 - 1 5/9 = 4 9/9 - 1 5/9 = 3 4/9

3) 3 4/9 · 21/31 = 31/9 · 21/31 = (1·7)/(3·1) = 7/3 = 2 1/3

ответ: 2 целых 1/3.