A plumber charges 80 for a service call plus 30 per hour a F

A plumber charges $80 for a service call plus $30 per hour.

a. Find a linear function that represents the total daily charges C, in dollars, as a function of the time t, in hours, spent at a given location.

b. If the total charge was $140, how many hours did he work?

Let t be number of hours he worked

So cost for t hours = 30t

additionally $80 for a service call

So we have f(t) = 80+30t

Given total charge is $140

So 140 = 80+30t

60 = 30t

t = 2

So plumber worked for 2 hours.