......1........3...........2........4.....
(7/8 - 4/5) + (1/20 + 1/4) + 1/2
1) 7/8 - 4/5 = 35- 32/40 = 3/40
2) 1/20 +1/4 = 1+ 5/20 = 6/20 = 3/10
3) 3/40 + 3/10 = 3+12/40 = 15/40 = 3/8
4) 3/8 + 1/2 = 3+4/8 = 7/8 = 0,875
Вроде все, надеюсь, помогла :3
Удачи :3