Answer:
The plumber worked 50 hours, and his assistant worked 25 hours.
Explanation:
Since a plumber and his assistant work together to replace the pipes in an old house, and the plumber charges $ 30 an hour for his own labor and $ 20 an hour for his assistant's labor, and the plumber works twice as long as his assistant on this job, and the labor charge on the final bill is $ 2000, to determine how long did the plumber and his assistant work on this job the following calculation must be performed:
40 x 30 + 20 x 20 = 1200 + 400 = 1600
50 x 30 + 25 x 20 = 1500 + 500 = 2000
Therefore, the plumber worked 50 hours, and his assistant worked 25 hours.