* when neither of them could figure out how the get the answer in the key.*
It's possible that the answer in the key was wrong. I spent a few years volunteering for RFBD.org, reading math & science textbooks a few hours a week, and many of the texts had answers in the back which frequently were not for the question in the front.
Unfortunately that was not the case. She just had to rely on the smarter students to help her. Then they hired us (woohoo 4.15/hr) to come tutor the algebra class after school three times a week while we were in high school. Almost every algebra student came to the tutoring session most of the time. The teacher never showed up once.
It's possible that the answer in the key was wrong. I spent a few years volunteering for RFBD.org, reading math & science textbooks a few hours a week, and many of the texts had answers in the back which frequently were not for the question in the front.