Read the word problem below. Antonio has a total of 55 marbles. He has 15 green marbles and 12 red marbles. The rest of the marbles are blue. How many blue marbles does he have?

A student solves this problem by writing an equation. Which strategy could help check the student’s answer?

a) Check that the sum of the final answer, 12, and 15 is 55.
b) Check that the difference of 55 and the final answer is 12
c) Check that the sum of the final answer, 27, and 15 is 55.
d) Check that the difference of 55 and the final answer is 15.