For this equation to be true 4^(n+4) should be just greater than 960 or in other words should be as close as possible to 960 and exceeding it. It's known that 4^(5) = 1024 therefore corresponding to this

**n = 1** which means the given equation becomes

4^(1+4) - 4^(1+2) = 1024 - 64 = 960.