Hi ! I'm trying to solve this problem. Though I get around to solving it by trial and error. The answer btw is 4.61 % ... But I am wondering ... Can this problem be solved other than trial and error method ?

Problem:

A piece of machinery can be bought for $10,000 cash, or for $2,000 downpayment and payments of $750 per year for 15 years. What is the annual interest rate for the time payments ?