Answer
Find out the how much did each computer cost before finance charges .
To proof
Let us assume that the price of the desktop computer be x .
Let us assume that the price of the laptop computer be y .
As given
the laptop cost $450 less than the desktop.
than the equation is written
y = x - 450
As given
He paid for the computers using two different financing plans.
For the desktop the interest rate was 7% per year,
the laptop it was 5.5% per year.
The total finance charges for one year were $279.
7 % is written in the decimal form
= 0.07
5.5 % is written in the decimalform
=0.055
than the equation becomes
0.07x + 0.055y = 279
simplify the above
we get
70x + 55y = 279000
put y = x - 450 in the equation
we get
70x + 55 ( x - 450 ) = 279000
70x + 55x - 24750 = 279000
125x = 303750
x = $ 2430
put in the y = x - 450
y = 2430- 450
y =$ 1980
Therefore the desktop cost $ 2430 before finance charge.
the laptop cost $ 1980 before finance charge.
Hence proved