Bob bought a desktop computer and a laptop computer. Before finance charges, the laptop cost $300 less than the desktop. He 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 6% per year. The total finance charges for one year were $398. How much did each computer cost before finance charges?

Laptop = $2,900

Desktop = $3,200

Explanation:

The cost of the laptop will be represented by the variable X

The desktop costs $300 more than the laptop, therefore, its cost will be X+300

The finance charge of 398 comes from the 7% interest on the desktop (7% interest on X+300), and the 6% interest on the laptop (6% interest on X).

We can lay out the formula with the information above:

398 = 0.07 * (X+300) + 0.06*X

398 = 0.07X + 21 + 0.06X

398 = 0.13X + 21

398 - 21 = 0.13X

377 = 0.13X

377 / 0.13 = X

2,900 = X

So X is the laptop, therefore, the laptop costs $2,900.

The desktop costs $2,900 + $900 = $3,200