15:24 is divisible by 3, simplifying it down to 3:8. 19:24, 7:8, and 6:8 are all obviously larger than this ratio, and 1:2 can be equalized to 4:8, which is also bigger than 3:8, so none of the answer choices are less than 15:24.
16 because 3 divided by 8 is 0.375 and 6 divided by 0.375 is 16.
