Achild has 48 quarters and 80 dimes. the child wishes to stack the coins so that each stack has the same number of coins, and each stack contains only one kind of coin. what is the
largest number of coins that the child can place in each stack?

Since the greatest common factor for 48 and 80 is 16 then we conclude the largest number of stack is 16

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)