Question 125156
Suppose you are starting an office cleaning service. You spent $315 on equipment. To clean an office you use $4 worth of supplies. You charge $25 per office. How many offices must you clean to break even? 
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Let "x" be the number of offices you clean.
Expenses: 315+4x dollars
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Income: 25x dollars
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EQUATION:
Break even means expenses = income
315+4x = 25x
21x = 315 
x = 15 (# of offices you need to clean)
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Cheers,
Stan H.