first, convert the mixed fraction into an improper fraction
15 10/7 = 265/17
265/17 divided by 5 is the same as 265/17 times 1/5
since 265 is divisible by 5, you can simplify the problem by cancelling out the 5 in 1/5 and dividing 265/5 in 265/17.
265/5=53
53/17