Milli plans to rent a room for her birthday party for $40. The catering charge is $12 per person but there is no charge for Milli's meal since she is the guest of honor. If Milli has $100 to spend on her birthday party, how many guests can she invite?
Well the room is $40 so take $40 away from $100 so Milli has $60 left to spend. If she invites 2 guests that would cost 24 dollars and 4 would cost 48 dollars. and 1 more guest costs 12 which would be adding 12 to 48 which would be 60 dollars spent if she invited 5 guests. so 12 x 5 = 60. so Milli could invite 5 guests.
Since she can spend 100$ but has already spent 40$ on the room, you do 60/12 to get 5. So she can invite 5 people.