Is it true that $\log_2 13$ is irrational?
Let $x=\log_2 13\implies 2^x=13$.
So, it will be an irrational number, if not,$$x=\frac p q$$
and $$2^{\frac p q}=13$$
$$\implies 2^p=13^{q}$$
Since, $13$ is a prime number, $2^p$ divides $13^q$.
So, $2$ divides $13$, which is absurd.
Is this reason worthy? Can you give some other proofs for this?
You are done in your solution at the step where you concluded that $2^p = 13^q$. You only need to quote Fundamental Theorem of Arithmetic after that step.