I'll give the same answer, hopefully in a little more understandable form. You want to end up with an equation that has x on one side and a number on the other. So, first get rid of the extraneous numbers by adding 15 to each side, 15 + -15 = 0, so now you have 16x - 9x = 28. Subtract the 9x from the 16x to get 7x = 28. To get x by itself you divide both sides by 7 to get 7x / 7 = 28 /7 or x = 4.