Answer:
6 minutes
Step-by-step explanation:
So for each minute, you would add 2 to your number while increasing your friends number by one.
You'd have 2 problems done when your friend would have 7, then 4 when they're at 8, 6 at 9, 8 at 10, 10 at 11
Then finally when it's been 6 minutes, you'd both have 12 minutes done.