The square of 9 less than a number is 3 less than the number. What is the number?

Let the number be x. “The square of 9 less than a number” is (x − 9)², and “3 less than the number” is x − 3. Solving (x − 9)² = x − 3 gives x² − 19x + 84 = 0, which factors as (x − 7)(x − 12) = 0. Thus the number is 7 or 12, matching choice D.

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