Answer:
Lindsay bought 3 pants
Explanation:
Lindsay went shopping at her favorite store. 
She bought 
- 4 shirt for $50 each and paid $200 for 4 shirts;
 - 2 purses for $30 each and paid $60 for 2 purses;
 - x pants for $40 each and paid $40x for x pants. 
 
Thus, her total bill was 

If her total bill was $380, then

Lindsay bought 3 pants