yaaanochka 45-у=40  -у=-5    у=5
24+х=31  х=7

3031978l (45-Y)+18=58
45-Y+18=58
-Y=58-45-18
-Y=-5
Y=(-5):(-1)
Y=1
(24+X)-21=10
24+X-21=10
X=10-24+21
X=7