add 91 to the other side to cancel it out-
37-91+3x=42
+91 +91
____________
37+3x=133
subtract 37 from the other side to cancel it out
37+3x=133
-37 -37
_________
3x=96
then divide 96 by 3 to get x by itself
3x=96
3 3
once you get x alone it should equal 32
x=32