21/6: 1 2/3-8 1/7•2 4/19+8 4/5 решите

2 1/6 : 1 2/3 - 8 1/7 * 2 4/19 + 8 4/5 = - 7 9/10

1) 2 1/6 : 1 2/3 = 13/6 : 5/3 = 13/6 * 3/5 = (13*1)/(2*5) = 13/10 = 1 3/10 
2) 8 1/7 * 2 4/19 = 57/7 * 42/19 = (3*6)/(1*1) = 18
3) 1 3/10 - 18 = - 16 7/10
4) - 16 7/10 + 8 4/5 = - 16 7/10 + 8 8/10 = - 7 9/10 = - 7,9
ответ: - 7 целых 9/10.