Have you tried taking the logarithm of both sides? If you don't know what base to use, don't choose one, just use 
to mean the logarithm of 
to base 
. You will see later that the base you choose is irrelevant.
We will need a couple of properties of logarithms in order to fully solve this, but the most important one is this:
If we apply this rule to remove the exponent on the lhs we get 
, similarly the rhs is 
.
The resulting equation is actually linear in a, so you should be able to rearrange the equation so that it looks like 
where 
are expressions in terms of logarithms to base b of numbers.
You can then get an exact expression for a, 
.
This expression still has a in it, but if you try with different values of you should find you always get the same answer.
See if you can use some of the other properties of logarithms to show that the results will always be the same regardless for what value of 
that you choose.
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