Spot the Mistake in a Worked Math Solution

Math Mistake Lab has four short sets of arithmetic and fraction problems. Each worked solution contains a first incorrect line; later lines may carry that error forward. Choose where the reasoning first slips to reveal a corrected step, explanation and final answer. These are fixed practice examples, not a checker for your own homework.

How to use Math Mistake Lab

1. Choose addition and subtraction, multiplication and division, fractions, or order of operations, then start the three-problem set.
2. Read the worked lines in order and select the first incorrect one. You can reveal a solution if you are stuck.
3. Compare the corrected line and explanation with your choice, then continue to the next problem or restart the set.