Dorothy bought two computers, one desktop and one laptop. Before finance charges, the laptop cost $500 more than the desktop. Dorothy paid for the computers using two different financing plans. For the desktop the interest rate was 7.5% per year, and for the laptop it was 7% per year. The total finance charges for one year were $796.25. How much did the desktop computer cost before finance charges?

Let x, y are the costs of laptop, desktop.

x=500+y.

0.075y+0.07x=796.25.

0.075y+0.07(500+y)=796.25.

0.145y=796.25-0.07*500.

y=761.25/0.145

=$5250.

x=500+y=$5750.

cost of desk top computer =$5250.