1. The problem statement, all variables and given/known data A car dealer sells a new car for $18,000. He also offers to sell the same car for monthly payments of $375.00 for five years. What monthly rate is this dealer charging? 2. Relevant equations A = [R(1 - (1 + i))^-60] / i where A = the present value, R = the monthly payment, i = the interest rate, n = the number of monthly payments Replacing i by x, show that 48x(1 + x)^60 - (1 + x)^60 + 1 = 0. 3. The attempt at a solution I thought that, "Replacing i by x, show that 48x(1 + x)^60 - (1 + x)^60 -1 = 0.", seemed to suggest that they wanted me to solve for i (or x), but in hindsight I don't think that's what I need to do. I don't know where to start now.  Or I suppose rather that I'm just supposed to set it equal to 0 somehow. In which case I guess I don't know what they're doing to (1 + x)^60.