Question 619971
let us call the number of hours on the job as 'h'

For each company the cost of a job is the initial house call fee plus the hourly fee multiplied by the number of hours on the job.
For Fif the cost of a job can be written as 25 + 50h
For DiR the cost of a job can be written as 35 + 45h

For each fee to be equal we can write it as follows:

25 + 50h = 35 + 45h

rearrange, remembering to change the sign if the value moves to the other side of the equation:

50h - 45h = 35 - 25

5h = 10

solve for h by dividing both sides by 5:
5h/5 = 10/5

h=2
so the number of hours on a job for the cost to be the same is 2 hours.

To check we can substitute the value of h into the equations for each company and see if they are the same:
For Fif the cost of a job can be written as 25 + 50h = 25 + 2(50) = 125!!!
For DiR the cost of a job can be written as 35 + 45h = 35 + 2(45) = 125!!!