They decided to hold the party in their backyard. They have 3 sets of tables and each set has 2 chairs. There are also 4 chairs extra. How many chairs do they have for the guests?
There are 3 sets of tables and each set has 2 chairs. 
That means that there are 3 times 2 chairs, or 6 chairs in total. 
There are also 4 chairs extra. 
That means that in total, they have 6 + 4 chairs, or 10 chairs for the guests.