12 13/45-(y-5 17/45)=3 23/45 с проверкой

12 13/45 - y + 5 17/45 = 3 23/45
17 30/45 - y = 3 23/45
y = 17 30/45 - 3 23/45
y = 14 7/45

12 13/45 - (14 7/45 - 5 17/45) = 3 23/45
12 13/45- (13 52/45 - 5 17/45) = 3 23/45
12 13/45 - 8 35/45 = 3 23/45
11 58/45 - 8 35/35 = 3 23/45
3 23/45 = 3 23/45