First find the cost of the ticket and the entrée for each person: $50/person + $10/person = $<<50+10=60>>60/person
Then multiply that cost by the number of people to find the total cost of entrees and tickets: $60/person * 6 people = $<<60*6=360>>360
Now find how many people ordered drink tickets: 6 people / 2 = <<6/2=3>>3 people
Now find the total cost of the drink tickets: 3 people * $30/person = $<<3*30=90>>90
Now find the total cost of the evening: $90 + $360 = $<<90+360=450>>450
Now multiply this quantity by 90% to find the amount of the refund: $450 * .9 = $<<450*.9=405>>405
Now subtract the refund amount from the total cost to find how much money the friends lost: $450 - $405 = $<<450-405=45>>45
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