Question 1136081
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You can solve this by logical reasoning, although algebra can also be used.<br>
Suppose Mary answers the first 4 questions right; then her score is 24 -- the score she ends up with.<br>
For her final score to again be 24, the remaining 16 questions must be half right and half wrong -- i.e., 8 right and 8 wrong.<br>
So overall she got 12 answers right and 8 wrong.