Answer :

AL2006
You divide each side of the equation by 4 .
Then you have

x = 15/4  or  3.75
Yeah AL2006 was right you have to divide 4 on both sides because when a variable is connected to a number like that with no sign between them it is multiplication and the opposite of multiplication is division and 4 divided by 4 cancels out because it is 0. 15 divided by 4 is 3.75.