Answer:
The mistake that Andy made was on step 2 when he multiplied only the variables by 12.
Explanation:
When you're solving an equation and are multiplying one side by a number, you need to multiply the other side by that number as well to keep the equation true. Since Andy multiplied only the variables and not the constants on each side of the equation, that means the equation would no longer be valid, and solving it would provide a wrong answer.