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from 1:we can conclude that the value of 'u' may be 3,5,7,9.........
since x,y given to be positive integers.
hence we cannot conclude or get the values of x and y from where we cannot get the gcd.
option E is the wright answer.

S1: x = 12u, where u is an integer. This tells us that: 12u = 8y + 12 ---> 3u = 2y + 3 ---> 3(u-1) = 2y ---> u = (2y)/3 + 1. Because this can give multiple values for x ---> INSUFF.

S2: y = 12z, where z is an integer. This tells us that: x = 8(12z) + 12 ---> x = 12(8z +1). From this it follows that, for all values of z (and thus y), the greatest common factor is 12 ---> SUFF.