From what I understand is that you have to multiply both sides by $2$, so that on the left side 2 cancel out and you are left with 3(t-7)
but why does right side turn into 2t-12?
So now you have:
3(t-7) = 2t-12
3t-21=2t-12
t-21=-12
t=9
I think it's right.