You must first attach the problems with your question.
Answer:
20 friends
Step-by-step explanation:
9 FRIENDS
2 HOURS
10 PEOPLE
2 HOURS
30 PEOPLE
2 HOURS
WORKS :D
Sorry if this is a little weird I did it the way I did it but I know the answer is correct. The work may not seem right to you -.- but :D I understand it...