PSAT Math Multiple-Choice Practice Question 97

Correct Answer: B

Explanation:

B

The question asks for an equivalent form of an expression. There are variables in the answer choices, so plug in. Since y must be greater than 3, make y = 4. The expression becomes , which is . To subtract fractions, make the denominators the same. One common denominator of 7 and 8 is 56. Multiply the numerator and denominator of by 7 to get . Multiply the numerator and denominator of by 8 to get . The expression becomes , which is . To divide by a fraction, multiply the numerator by the reciprocal of the denominator to get 1 × or -56. This is the target value; circle it. Now plug y = 4 into the answer choices to see which one matches the target value. Choice (A) becomes 3 - 4 or -1. This does not match the target, so eliminate (A). Choice (B) becomes , which is . Multiplying gives , which is -56. Keep (B) but check the remaining answer choices just in case. Choice (C) is the reciprocal of (B), so it will equal . Eliminate (C). Choice (D) is the numerator of (B), so it will equal 56. Eliminate (D). The correct answer is (B).