Ineed with #7, i am not sure how to solve it and what interval means

Find solutions between the intervals
-3, -2, -1, 0, 1, 2, 3

You got the basic idea how to solve it but:

when you have 2^-3, it's not -8
2^-3 = 1/2^3 = 1/8
same goes with -2 and -1

When you have negative power you basically divide n^-x = 1/n^x