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, what is the maximum number of friends Milli can invite?

This is a 2 part question. 

Milli has $100 to spend and pays for the room first. $100 - $40 = $60 to pay for meals.

Each meal is $12 - how many meals can she buy with $60? 

60 / 12 = 5 meals 

So Milli and 5 friends can be at the party. 

To check: 5($12) + $40 = $100