Piper has a balance of $1,500 on her credit card with a 21% interest rate. Piper will make payments of $79.54 for 24 months to pay off the card. How much will Piper pay in interest?

Problem number 26 of the rhind papyrus says: find a quantity such that when it is added to of itself the result is a 15. the modern day equation that models this problem is x + x = 15. what is the solution to the equation? x = 10 x = 12 x = 15 x = 30