(6x-27)=(3x+15) You have to isolate the variable so in anyway possible you have to get all number to one side and the variable and their coefficient to the other side. 3x/3x and 6x/6x leaves you with (2x-27)=(15) Next you can add 27 to each side to get rid of the 27 with 2x leaving the problem at 2x=42 Then divide by two 42 divided by 2 is 21 So x=21