one way is to make the first equation negative and add it to the first equation so
-(3x+y=2)
-3x-y=-2
add to 4x+y=20
4x+y=20
-3x-y=-2+
1x+0y=18
x=18
subsitue
3x+y=2
3(18)+y=2
54+y=2
sutract 54 from both sides
y=-52
x=18
y=-52
solution in point form or (x,y) form is
(18,-52)