If I've understood your question, you're asking about this:
[tex] \frac{4}{3^{-2}} [/tex]
A number raised to a negative power is the same as the inverse of that number raised to the positive power. Basically the number moves from the numerator to the denominator or the denominator to the numerator. So 1/(3^-2) is the same as 1 / (1/3^2), which is the same as 3^2. That means what you have here is 4 x 3^2, which is 36.
