Answer
The plumber makes 50 dollars an hour, the laborer makes 10 dollars per hour, and the apprentice makes 20 dollars per hour.
Work Step by Step
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$
