To solve for x, you need to isolate/get the variable "x" by itself in the equation:
-3x + 2 = 2x + 37 Add 3x on both sides to get "x" on one side of the equation
-3x + 3x + 2 = 2x + 3x + 37
2 = 5x + 37 Subtract 37 on both sides (you could have subtracted 2x instead of adding 3x, and subtract 2 instead of 37)
2 - 37 = 5x + 37 - 37
-35 = 5x Divide 5 on both sides to get "x" by itself
-7 = x
PROOF
-3x + 2 = 2x + 37 Substitute/plug in -7 into "x" since x = -7
-3(-7) + 2 = 2(-7) + 37 (two negative signs cancel each other out and become positive)
21 + 2 = -14 + 37
23 = 23