Concept: The question tests on the application of exponents and equation in a DS format.

Solution:

2x+y = (22)8 = 216

x +y = 16

 St (1) x2 = 81 and thus x = 9, - 9

Hence y = 7, 25 

No unique value of y is obtained.  Insufficient

 

St (2) x-y =2 

Along with x + y =16 (given) a unique value of y = 7 can be obtained.

Thus Sufficient.

 

Hence option (b)