Question

 plumber and his assistant work together to replace the pipes in an old house . the plumber charges $45 per hour for his own work and $25 for his assistant's labor. the plumber works twice as long as his assistant on this job, and the labor charge on the final bill is $4035. how long did the plumber and his assistant work on the job?

Answer 1

$45 per plumber hour (p)
$25 per assistant hour (a)
$4035 = 25a + 45p
p = 2a

4035 = 25a + 45(2a)
4035 = 25a + 90a
4035 = 115a
a = 35.086 hours
p = 2(35.086)
p = 70.174 hours

The plumber worked about 70 hours, and his assistant worked about 35 hours.