Do the subtraction first, then look at the differences among solutions to find the errors.
Neither Cheyenne nor Sebastian are correct. Explaination: See solution.
Practice makes perfect
For this exercise we need to analyze two solutions to see if they are correct. One way to do this is to complete the process ourselves, then compare answers.
Our answer matches neither of the two answers shown. Let's look more carefully at Cheyenne's solution, then Sebastian's.
It looks like Cheyenne made a mistake in the distribution of the - 1. She only distributed to the first term, neither the 3x^2 term nor the -2 term changed signs as they should have.
In Sebastian's case, he get's the incorrect answer because he also did not distribute the -1 appropriately. In conclusion, both people distributed incorrectly.
