# Chapter 11 - Additional Topics - 11.2 - 3 x 3 Systems of Equations - Problem Set 11.2 - Page 484: 21

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: $a = 80 - p -l \\ a = 80 - 50 - 10 = 20$

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