To see how many integers from 15 to 85 are multiples of 8, one way would be (probably not the most efficient way) to list all of the numbers out that are multiples of 8 and are from 15 to 85.
16, 24, 32, 40, 48, 56, 64, 72, 80
Those are all of the integers from 15 to 85 that are multiples of 8. Now, to find our answer, we have to count them. Counting them, we get 9, so there are 9 multiples of 8 from 15 to 85.