7/20 · 9 + 12 · 7/36 + 1 8/15 : 4 + 3/5 : 4 1/2 = 6
1) 7/20 · 9 = 63/20 = 3 целых 3/20
2) 12 · 7/36 = 1 · 7/3 = 7/3 = 2 целых 1/3
3) 1 8/15 : 4 = 23/15 · 1/4 = 23/60
4) 3/5 : 4 1/2 = 3/5 : 9/2 = 3/5 · 2/9 = (1·2)/(5·3) = 2/15
5) 3 3/20 + 2 1/3 = 3 9/60 + 2 20/60 = 5 целых 29/60
6) 5 29/60 + 23/60 = 5 52/60 = 5 целых 13/15
7) 5 13/15 + 2/15 = 5 15/15 = 6