3x+y=8
x-3y=33
Times the bottom equation by 3 so you get the same coefficient of x
3x+y=8
3x-9y=99
Subtract the bottom equation by the top to find y
y- -9y is y+9
10y=-91
So y is -91/10
Now substitute y into an equation so
3x-91/10=8
-91/10 is -9.1
3x-9.1=8
Plus 9.1 to each side
3x=17.1
x=5.7 or 57/10