To do this, we just have to add as if we were adding regular numbers. 3p+5p= 8p. To add the next p, we have to pretend that there is a one right in front of it. Indeed, there is a one in front of the p, but most people and most math problems don't put the one there. But anyways, 8p+1p=9p. Your answer is 9p.
3p + 5p + p = 9p. When you have the variable on it's own, it is 1. When you have like variables, the will combine, so 1p + 3p + 5p = 9p.
