1. There's no equation given to solve. Equations have an equal sign (=) in them.
2. What is CE meant to represent?
3. Is e-3at meant to be . If so, it should at least be written as e^(-3at).
4. "I have replaced t with t= [(t-2T)+2T]" makes no sense.
If you want help, especially urgent help, you will need to be much much clearer.