Question

`A(x)=3^2`

If 81 came out, what was dropped in?
I have rewritten the problem to
`3^x=81` but do not know how to solve it.

Answer 1

`A(x)=3^x=81\\ 3^x=81\\ 3^x=3^4\\ x=4`

Answer 2

It is good equation. Look, that:
81 = 3 x 3 x 3 x 3 = 3^4.
So you have to solve:
3^x = 3^4
exponents have to be the same, so
x=4
That's mean that A(4) = 81