As I understand this post, the visitor asks to check if his (or her) solution is correct.
-3*(t-2) = 12
-3t + (-3)*(-2) = 12
-3t + 6 = 12
-3t + 6 - 6 = 12 - 6
-3t = 6
Divide both sides by (-3)
t =
t = -2.
ANSWER. t= -2.
CHECK. Substitute t= -2 into the given equation. You will get in the left side
-3*((-2) -2) = -3*(-4) = 12. ! Correct !