Bobby borrowed $500 at 12 percent simple annual interest. he paid back $680 to pay off the loan. how many years did it take bobby to pay back the loan?

Amount = $680

Principal = $500

Interest = 680 - 500 = 180

Rate = 12% Simple annual interest.

I = PRT

180 = 500*12% * Time

180 = 500 * 0.12 * T

180 / (500*0.12) = T

3 = T

T = 3 years.

It took Bobby 3 years to pay back the loan.  

It has a slope of 1 nd a y intercept of -2