Concept: The question tests on basics of Number Properties
If x = 749 and y = 1, then the HCF is 1. This is the minimum possible value.
To get the maximum value of the HCF, we divide 750 by 2 which is x = 375 and y = 375 and the HCF will be 375.
The difference is therefore 375 - 1 = 374