Let's add the fractions first and then we can estimate the sum.
= 31/4 + 17/3 + 8/18
change to common denominators
= 279/36 + 204/36 + 16/36
add numerators only
= 499/36 or 13 31/36 or 13.86
ANSWER: (B) 13 is the best estimate of the answer. Normally we round up to 14 with a number like 13.86, but since that is not a choice, we can estimate 13 as the answer.