They decided to hold the party in their backyard. They have 11 sets of tables and each set has 47 chairs. There are also 8 chairs extra. How many chairs do they have for the guests?
There are 11 sets of tables and each set has 47 chairs. 
That means that there are 11 * 47 = 517 chairs in total. 
There are also 8 chairs extra. 
That means that there are 517 + 8 = 525 chairs in total.