A negative exponent means that factor is on the wrong side of the fraction, so the 4^-7 in 4^2/4^-7 should be moved to the top. When you move it to the other side, the exponent turns from negative to positive:
4^2/4^-7 = 4^2•4^7/1
What’s 4^2•4^7? How many 4’s are multiplied there?
There’s two 4s followed by seven more 4s, for a total of nine 4s: 4^9