Twilight sparkle was throwing a pony party at her house. Rainbow Dash stood outside to see how many ponies were going attend the party. She saw this happen in this order.
3 ponies entered the house together.
1 COMrade entered the house.
4 more ponies entered the house.
Twilight Sparkle then left the house temporarily, and came back into the house with Applejack
When the party was over 10 ponies then left the house.
Rainbow Dash then went inside the house to find that the house was completely empty!
How could this be?