Answer:
Option C)
Explanation:
We are given the following information in the question:
Number of jeans in inventory = 688
The store manager decides to reduce the the stock by giving a buy one get one free scheme. That means that every purchase will reduce this inventory by 2 pairs of jeans.
This can be represented with the help of equation:

where x is the number of jeans purchased.
In the above expression the term 2x is the total number of jeans sold, where x is the number of jeans sold. Due to buy one one free offer the jeans reduced from the inventory are double the jeans sold.
Thus, 2x in the equation means that every purchase will reduce the inventory by 2 pairs of jeans where x is the number of purchases.