21,4 - 5 1/2 - (16 2/3 - 6,6) = 5 5/6
1) 16 2/3 - 6,6 = 16 2/3 - 6 3/5 = 16 10/15 - 6 9/15 = 10 1/15
2) 21,4 - 5 1/2 = 21,4 - 5,5 = 15,9 = 15 9/10
3) 15 9/10 - 10 1/15 = 15 27/30 - 10 2/30 = 5 25/30 = 5 5/6
ответ: 5 целых 5/6.
