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algebra intermediate

Problem

For each plumbing repair job, Mr. Wrench charges dollars for coming out to the house plus dollars per hour that he works at the house. He charged \97\ for a five-hour repair job. What is his charge for a two-hour repair job?
Solution
We can rewrite the problem as the system of equations: Subtracting these gives: So now . So the charge for a two-hour repair job is N+2x = \ 55+2\cdot \42 = \boxed{\ 139}$.
Final answer
\$ 139