Kohl's sells casual shirts for $9 and polo shirts for $18.00. Total sales were $1,080, and customers bought 4 times as many casual as polo shirts. How many casual shirts did Kohl's sell?

Let x be the number of polo shirts customers bought

4x be the number of casual shirts bought by customers

Based on the condition that the total sales amounted to $1,080, the equation becomes

9 (4x) + 18 (x) = 1,080

This equation gives a value for x equal to 20.

Therefore, Kohl's sold 80 casual shirts.