Question 56613
A building hold 80 apartments. Une bedroom apartment cost $850/month. A two bedroom apartment cost 1050/month. The location itself cost 78200/month. How many one bedrooms and two bedrooms are in this building? 
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Let number of one bedroom be "x"; cost of these is 850x dollars.
Number of two bedroom is "80-x; cost is 1050(80-x)=84000-1050x dollars
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EQUATION:
cost + cost = 78200
850x + 84000-1050x = 78200
-200x=-5800
x=29 (number of one-bedroom apartments)
80-x=51 (number of two-bedroom apartments)
Cheers,
Stan H.