Lisa, Jack, and Tommy earned $60 from washing cars all week. However, half of the $60 was earned by Lisa. Tommy earned half of what Lisa earned. How much more money did Lisa earn than Tommy?
Thoughts? Step-by-step reasoning:
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Lisa earned $60 * 1 / 2 = $30. Tommy earned $30 * 1 / 2 = $15. Lisa earned $30 - $15 = $15 more than Tommy.
Thus, the answer is 15.
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