12-y=15
Add y to both sides to get: 12=15+y
Then -15 to both sides to get (this way you have y on one side and the numbers on one side): 12-15=y
y=-3
12-y=15
=12-15=y
=y=-3
first we shift y on right by changing hi sign negative to positve
12 = 15 + y
then we subtracted 15 on both sides we get
12 - 15 = 15 - 15 + y
-3 = y
y = -3 answer.