Math: Algebra

SAT Question of the Day for October 8, 2026

For what value of kk does the equation 3(2x+k)=6x+93(2x + k) = 6x + 9 have infinitely many solutions?
  1. A.99
  2. B.33Correct answer
  3. C.66
  4. D.−3-3

Explanation

Distributing on the left gives 6x+3k=6x+96x + 3k = 6x + 9. For the equation to be an identity (true for all xx), the constant terms must be equal: 3k=93k = 9, so k=3k = 3. The value 9 results from failing to divide by 3 and equating kk directly to 9. The value 6 reflects a conceptual error about the relationship between coefficients and constants. The value −3-3 results from a sign error when dividing 9 by 3.

How to use this question

Try the question before you read the explanation: cover it, commit to an answer, and then compare your reasoning with the worked solution. If you missed it, note the step where your approach went wrong rather than only the correct letter, and look for that same step the next time you see a similar question.

Every past question stays here with its answer and explanation, and a new question is posted every day.

Try today's question

A new SAT practice question is posted every day, free and with no account needed.

Answer today's question