Question

−12.7 = y − 3.4. What does y equal?

Answer 1

−12.7 = y − 3.4
-y = -3.4 + 12 .7
-y = 9.3
y= +9.3
(because our signs change when we change their places to the other side )

Answer 2

y= -9.3
First, you must add 3.4 on both sides of the equal sign.
When you do this you're left with -9.3=y