.
x dollars for the desktop; (x+450) dollars for the laptop.
Write one year total finance charges equation
0.09*x + 0.06*(x+450) = 300 dollars.
Simplify and find x.
etc.
The rest is simple arithmetic.
------------------
To see many other similar solved problems using one equation in one unknown, look into the lesson
- Typical investment problems
in this site.
To see many other similar solved problems using systems of two equations in two unknowns, look into the lesson
- Using systems of equations to solve problems on investment
in this site.