The McDonalds are purchasing a new refrigerator.

Question

The McDonalds are purchasing a new refrigerator. They find two models that fit their needs. Model 1 sells for $575 and costs $0.07 per hour to run. Model 2 is the energy efficient model that sells for $825, but only costs $0.04 per hour to run. If x represents number of hours, then the costs to purchase and run the refrigerators are modeled by the equations
C1(x) = 575 + 0.07x

C2(x) = 825 + 0.04x

If the McDonalds buy Model 2, how many hours must it run before they save money? How many days must it run before they save money?

Answer 1

The question asks at what time, x, is 

575 + 0.07x > 825 + 0.04x

 

Can you solve for x?