brett is having a party .first guest arrived by himself,3 guests then arrive together,each successive group arrives with 2 more guests than the group that entered previously.How many guests will have arrived when the twentieth group enters the room? please explain, thanks
Anthony/Nicky/Jade/Karen -- please use the same name for your posts.
I've helped you with several problems. Now it's your turn.
I'll be glad to check your answer.