Key to correctly answering this question is noticing that the 1/3 for the registration and 1/3 for the insurance are not each 1/3 of his paycheck. They are each 1/3 of what remained after he spent 1/4 of the paycheck on repairs.
Question: Brian spent 1/4 of his paycheck to repair his car, and then paid the registration and insurance, which each cost 1/3 of the remainder of his paycheck. If Brian had $0 before he was paid, and he now has $231 left, what was the amount of his paycheck?
Brian spent 1/4 to repair his car.
1 - 1/4 = 3/4
Of what remained, or 3/4, he spent 1/3 on registration and 1/3 on insurance.
We can keep this simple.
1/3 of 3/4 is clearly 1/4.
So, for registration and insurance he spent 1/4 of his paycheck and 1/4 of his paycheck.
3/4 - 1/4 - 1/4 = 1/4
So, of his paycheck, he had left 1/4 = 231.
The whole check must have been 4 x 231 = 924.
The correct answer is (C).
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