Answer:
$800
Step-by-step explanation:
The ratio of 5:3:2 represents desks:cupboards:beds. This means that if we bought one set of this ratio we would buy 5 desks - 3 cupboards - 2 beds for a total of 10 items. If we buy 300 items and 10 is the number of items in one set, then we can buy 30 sets since 30*10=300. So in total we will buy 5 desks *30=150 desks. We will buy 3 cupboards*30=90. We will buy 20 beds*30=60 beds.
If desks cost $250 each, then 150 desks will cost 150*250=$37,500.
If beds cost $500 each, then 60 beds will cost 60*500=$30,000.
If cupboards cost ___x__, then 90 cupboards will cost 90x and be the remainder of the money. So we will find the cost of the cupboards by dividing the remainder of the money by 90. We subtract from the total 139,500-37,500-30,000=72,000. We divide 72,000 by 90 and get $800 for each cupboard.