Answer:
9 tables
Explanation:
Let x be the number of chairs sold and y be the number of tables sold.
Chairs are sold for $100 each, then x chairs cost $100x.
Tables are sold for $550 each, then y tables cost $550y.
Every day, the store can ship at most 21 pieces of furniture, then

Store must sell no less than $5,700 worth of chairs and tables, then

If 10 chairs were sold, then
Substitute this value into both inequalities:
1.

2.

Hence,

The minimum number of tables that the the store must sell in order to meet the requirements is 9 tables