An online furniture store sells chairs for $200 each and tables for $600 each.
Let the chairs be x and the tables be y
200 x + 600 y < 13000 --------------- equ 1
x + y = 39 ................................................equ 2
If x = 20 ,
200 ( 20 ) + 600 y < 13000
4000 + 600 y < 13 000
600 y < 13000 - 4000
600 y < 9000
Divide both sides by 600
y < 15
The minimum number of tables that the store must sell in order to meet the requirements = 15 tables.