## Elementary Algebra

Let p be the amount the plumber makes, l be the amount the laborer makes, and a be the amount the apprentice makes. Thus: $l + a + p = 80 \\ p = 5l \\ p = a + l + 20$ Substituting $p-20$ for $a+l$ in equation one, we find: $p -20 + p = 80 \\ 2p = 100 \\ p = 50$ We now use equation two: $l = p/5 \\ l = 50/5 = 10$ We now solve equation one for a: $a = 80 - p -l \\ a = 80 - 50 - 10 = 20$