Surface area of the sphere comprises two edges ( i.e., radius * radius)
Percentage decrease in each of the first and the second edge will be 50%, i.e., X% = Y% = 50%
And in case of the percentage decrease values of X and Y will be negative.
Change in surface area of the sphere
((-50)-50+((-50)*(-50))/100)% = (-100+25)% = -75%
Hence surface area of the sphere will be decreased by 75%