想请教

80. 7589-!-item-!-187;#058&005492

If x and y are positive integers such that x = 8y + 12, what is the greatest common divisor of x and y ?

(1)    x = 12u, where u is an integer.

(2)    y = 12z, where z is an integer

答案选B

能请各位帮我解答一下吗

(1)

12(u-1)=8y

3/2(u-1)=y get nothing

(2)

12(8z+1)=x

if z=1, greatest common divisor is 12

if z~=1, 8z+1 is not a multiple of z

so 12