A dress was initially listed at a price that would have given the store a profit of 20% of the wholesale cost. What was the wholesale cost of the dress?

A. After reducing the listed price by 10%, the dress sold for a net profit of $10.

B. The dress is sold for $50.

Let the initial selling price be s1 and changed value be s2, also wholesale cost price be c. According to the given condition we have s1=1.28*c. By statement A we have s2=0.9*s1 and s2-c = 10 . Hence, wholesale cost price can be found out.
Considering statement B we have just s2=50. Using this we can't find c. Hence, the question can be answered by one of the statements alone but not by the other.