Why $\frac{\log4}{\log b}$ can't be simplified to $\frac4b$? 
I want to know why $\frac{\log4}{\log b}$ can't be simplified to $\frac4b$. 

I am a high school student. Please do not quote some theories that are too advanced for me. Thank you!

Well, suppose you could do such simplification:
$$
\frac{\log 4}{\log b}=\frac{4}{b}\tag{1}
$$
You would end up with (do you know why?)
$$
b\cdot \log 4=4\cdot\log b,
$$
which implies (do you know why?) that
$$
\log 4^b=\log b^4\tag{2}.
$$
If (1) were true for every $b>0$, then (2) must also be true for every $b>0$ and in particularly true for $b=1$ which is $\log 4=\log 1$. But it is impossible. 
