My mom came home around six that evening. She dropped her books on the kitchen table and immediately went to get dressed for work. She studied three times a week at the community college. She wanted to finish her math degree, but didn’t have enough time to go the school full time. Or enough money. She worked the evenings as a nurse’s assitant, often working overtime.

Half an hour later, she was on her way out again, giving me a quick peck on the cheek, leaving me with instructions to give the twins dinner and not to let the stay up past nine.

After I put the twins to bed, I went back into the kitchen and started clearing away the dishes. Once I had put everything away and put the leftovers in the fridge, I started to move my mom’s things into the study. I tripped over an abandoned dinosaur toy and dropped the pile of books. As I started placing the pages back into their folders, I caught sight of a half-finished equation.

I studied it for a minute, working through the steps in my head.