I need help with this world problem

Question

Yoko bought a desktop computer and a laptop computer. Before finance charges, the laptop cost $250

 less than the desktop. She paid for the computers using two different financing plans. For the desktop the interest rate was 7% per year, and for the laptop it was 8% per year. The total finance charges for one year were $325. How much did each computer cost before finance charges?

Answer 1

Let L = cost of laptop, D = cost of desktop

L = D - 250 (cost of laptop IS 250 less than cost of desktop)

.07 D represents interest paid on desktop

.08L represents interest paid on laptop

.07D + .08L = 325 (total interest/ finance charges IS 325.

If you do not like working with decimals (like I do not), multiply each term of the previous equation by 100.

7D + 8L = 32500

Since L = D - 250 substitute for L in the previous equation.

7D + 8(D - 250) = 32500

7D +8D - 2000 = 32500

15D = 34500

D = 34500/15 = 2300

L = 2050

Check:

.07(2300) = $161

.08(2050) = $164

Total finance charge: $325