Question

The sum of the charges of the quarks in a particles gives the overall charge of the particles. Two up quarks and a down quark make a proton, which has a charge 1. On the other hand, two down quarks and an up quark make a neutron, which has a charge 0. What is the charge of an up quark?

I have no idea how to solve this. I'm assuming that I would make a system of equations, since that is what we're learning about. And what is a quark? Thank you so much!