Answer: The correct answers are 84% and 10,140.
Step-by-step explanation: In order calculate what percentage of seats were sold you need to divide the numer of seats sold by the total number of seats.
3,276 / 3,900 = 84% of the seats were sold.
If the hockey game sold 78% of the seats, it is calculated by multiplying 13,000 x .78 = 10,140 tickets were sold.