The average cost of airfare for a one-way ticket from Las Vegas to Los Angeles was $67 for the days of Monday through Friday. The cost of airfare Monday through Thursday was $40, $44, $50, $60 respectively. What was the cost of airfare on Friday?
If the average cost of the plane ticket for 5 days was $67, that means the sum of the costs is 5*67= $335. The first four days are given at $40, $44, $50, and $60. The sum of those is $194. The cost of the ticket on the last day would be $335-$194= $141.
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