Answer: 18
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Work Shown:
x = number of windows purchased
The cost expression is 145.50x+3150 because the "145.50x" portion represents the $145.50 per window charge, then we tack on the fixed fee of $3150. Set this cost expression equal to the total charge ($5769) and solve for x.
[tex]145.50x+3150 = 5769\\\\145.50x = 5769-3150\\\\145.50x = 2619\\\\x = 2619/(145.50)\\\\x = 18\\\\[/tex]
They bought 18 windows.
