Bunuel wrote:

What is the value of y−x?

(1) 3^y − 3^x is divisible by 10.

(2) y>x

(1) 3^y − 3^x is divisible by 103^y − 3^x = 10k.

3^x(3^(y-x) -1 )=10x.

3^x will not be divisible by 10. So (3^(y-x) -1 ) has to be divisible by 10.

a.One of the cases is x=y, so y-x=o.

b. Other case is when 3^(y-x) has its last digit as 1, so 3^(y-x)-1 will end in 0 thus divisible by 10. For this y-x should be a multiple of 4(Cyclicity of powers of 3). So y-x can be 4,8,12, and so on.

Not sufficient.

(2) y>x - Not sufficient.(1)+(2) - We can eliminate only case (a) mentioned above as y>x, yet case (b) itself has many values. - Not sufficient.

Answer - E

Cheers!