Thanks for your input Shadowdude.
I will try it out:
Let ϵ > 0, there exists δ > 0 such that for all x in reals and 0 < |x - 5| < δ we have, |(3x-3) - 12| < ϵ
Simplifying and collecting like terms, we have
|3x - 15| < ϵ
Dividing by 3 on each side
|x - 5| < ϵ/3
Now, setting δ = ϵ/3...