Information in the link below:
https://www.history.com/this-day-in-history/germany-resumes-unrestricted-submarine-warfare
On this problem you don't need to subtract. They want to know the total amount of people who attended so you would add.
1 1 1 (carried over numbers)
12,679 (Line it up with 8491, ones place to ones place and so on)
+8,491
21170 (answer)
Oh hi guys we will see what happens next to
Answer:
The british (The united Kingdom)
Explanation: