4^-7 is just 1/4^7 so this is equal to 4^2 divided by 1/4^7. Dividing by a fraction is the same thing as multiplying by its reciprocal (just flip the fraction). So this whole equation is equal to 4^2 multiplied by 4^7. And when you multiply two exponents with the same base, the exponents are just added. So, your answer should be 4^9. Hope this helps! :)
