do you subtract 15 to each side when the equation look like this 3=-3y-15
Do you subtract 15 to each side in this equation: 3=-3y-15
In Algebra, to undo an operation you perform the opposite operation.
and, remember--whatever you do to one side, you must do to the other side--
Thus you solve your equation--
since you want y by itself, you undo the multiplication by 3
divide both sides by 3
Actually, you need to add fifteen to both sides of the equation in order to remove it from that side of the equal sign. (Basically, you are doing -15+15=0 on the right side and 0+15=15 on the left.)
When working to try to get a variable by itself, you perform the inverse operation. The 15 is being subtracted from -3y, so the opposite is adding 15 to both sides.
3 +15 = -3y -15 +15