If solving for x:
Because both equations are equal to Y, you can set both equations equal to each other:
5x+1=4x+8
Then it's a matter of simplification (subtract the 4x to the left side and subtract the 1 over to the right):
x=7
If solving for Y:
Plug x=7 into either equation and solve:
Y=4(7)+8
Y=36