He truck is rented at $40 per day plus they charge per mile of use the truck travel 15 miles in one day and the total charge was 115 which equation can be used to find the x charge in dollars per mile traveled?

15x + 40 = 115

We set the equation to 115 because the total cost is $115.
We add the "+ 40" because of the $40 to rent the trailer for the day.
The 15x is because it represents the miles per hour (x) times the number of hours.

The number of hours times the charge per mile, plus the $40 to rent it, will equal $115.

Hope this helps!!