Решить пример (13 целых2/7÷31/70-28,5)÷6,75+20 целых2/3-19целых9/10

(13 2/7÷31/70-28,5)÷6,75+20 2/3-19 9/10= 89/90
1) 13 2/7:31/70 = 93/7*70/31 = 30
2) 30-28,5 = 1,5
3) 1,5:6,75 = 15/10:675/100 = 15/10*100/675 = 10/45 = 2/9
4) 2/9+20 2/3 = 2/9+62/3 = 2/9+186/9=188/9 = 20 8/9
5) 20 8/9-19 9/10 = 188/9-199/10 = 1880/90-1791/90 = 89/90