it is a word problem and I don't know how to plug the numbers in

Question

9. One car-rental company charges $42 per day with unlimited mileage. Another company charges $30 per day plus
15¢ per mile. You need to rent a car for a three-day trip. Find the break-even point, where the cost is the same for the two companies.

Answer 1

Cost from company A = $42*d      Let d = number of days car is rented = 3 days

 

Therefore, Cost from Company A = $42*3 = $126 to rent car for the 3 days

 

Cost from company B = $30*d + $0.15*m     Let m = number of miles

 for 3 days,

 

Cost from Company B = $30*3 + $0.15*m = $90 + $0.15*m

 

To find the break-even point where the costs are equal from both companies, you need to set them equal to each other and solve for the number of miles you can drive over the 3 days.

 

Therefore, Cost from B = Cost from A

 

$90 + $0.15*m = $126

 

Solve for m or miles allowed to drive to break even:

 

m = ($126 - $90)/$0.15 =  $36/$0.15 = 240 miles