x needs to be solved for, so we must isolate x. 

5x + 2 = 3x + 12  (subtract 2 from the left side)

5x = 3x + 12 - 2  (subtract 3x from right side)

5x - 3x = 12 - 2 (x is now isolated, add both sides)

2x = 10  (divide both sides by 2)

x = 5

You can check your answer by plugging 5 back into the orignial equation

5(5) +2 = 3(5) + 12

25 +2 = 15 + 12

27 = 27

Hope this helps & good luck!

To solve this, you first need to get all the x's on one side and all the numbers on the other. Then divide both sides of the equation by the number attached to the x.