So x is a variable which is just character representing a number. We want to find x. To do this we want to get X by itself on one side of the equation. In this case/ we just need to divide both side by -4. Whatever you do to one side, you must do to the other. This gives us X = -12. To check yourself just plug your answer back into the equation to see if its right. -4(-12) = 48. You have successfully solved for X.