This isn't a specific topic I need to know for school or something, Im just curious. I know the first three variable letters most commonly used are x, y, and z. But what if you have more variables, what would be the next letters to use? I have seen some places saying x, y, z, and t; others x, y, z, w, p, and r; and others p, q, r, s, x, y, and z but none seemed to have a definite answer and I don't know what to use.