Question 1034478
I will make the assumption that you actually meant a 23-watt CFL bulb to be $2.50 each. It doesn't make sense that each one costs $250.

Let x = number of 23-watt CFL bulbs purchased,
y = number of 42-watt CFL bulbs purchased.

With this in mind,you can come up with the system

2.50x + 8.25y = 1305,and
x + y = 200

Using Cramer's rule,

{{{x = abs(matrix(2,2,1305, 8.25,200,1))/abs(matrix(2,2,2.50, 8.25,1,1)) = 60}}},and 

{{{ y= abs(matrix(2,2,2.50, 1305,1,200))/abs(matrix(2,2,2.50, 8.25,1,1)) = 140}}}.  
Therefore 60 23-watt CFL bulbs were purchased, and 140 42-watt CFL bulbs purchased.