Answer:
3 hours
160 - 55 = 105
105 ÷ 35 = 3
Step-by-step explanation:
First, we must turn this into an equation:
35n + 55 = 160
N = number of hours
Next, solve:
35n + 55 - 55 = 160 - 55
35n = 105
n = 3
The plumber was there for 3 hours.
