Explanation:
T-8=12
simplify:
you have to get unknown values on one side and known numbers on another side.
+ you need to know that when we move anything to another side of =, it changes sign.
in our case we have to leave T in right side and move -8 on left side. as I said it changes sign when we move it to other side, so you will have T=12+8 and not T=12-8...
so let's continue:
T-8=12
T=12+8
T=20