Answer:
The answer is that 90 couples remain at the party after 11 pm
Explanation:
Number of people who went to the couples only party at 9 pm = 250
Number of people who left the party at 11 pm = 70
How many couples remained at the party?
People that remained at the party = 250 - 70 = 180
Couples that remained at the party = 180/2 = 90
The answer is that 90 couples remained at the party after 11 pm