You have to divide every number of there with 12 and the answer will have to be 8. So if you divide 20 % 12 would be 1.66666666667, which is incorrect just like the 1.5 % 12 because the result is 0.25 just like 84 % 12 because the result is 7. So, now that you see that the 3 first answer are wrong. The last is the correct, and not just because is the only one left. Is because if you divide 96 % 12 the answer is 8.