Answer: Hi! 
They initially had 200 white hats, which is the 100%, and they sold 120 of them. 
The percentage sold is the number of hats sold divided by the initial amount of hats, multiplied by 100% 
(120/200)*100% = 0.6*100% = 60% 
they sold 60% of the white hats. 
For the black hats the sold 120 out of 300, using the same reasoning as before, the percentage of black hats sold is: 
(120/300)*100% = 0.4*100% = 40% 
They sold 40% of the black hats, and as we know 40% < 60% 
 they sold a greater percentage of the white hats.