To obtain y, put everything up to the e. This will bring down y due to the rule of logs and that is your answer (assuming you've done the rest correct)
The value of constant is not same on both the sides. if you have written C on the left side, then express the constant on the right hand side with another letter. (say ). After that, bring all the constants on the same side. this gives you
note that , the difference of two constants, is also a constant. For convenience, denote it with another letter.
then find y