**CONCEPTS:** The question tests the basics of Average/A.M

**SOLUTION: **

Let the three numbers be (x-d),x,( x +d)

"d" is the space.

Average = (x-d)+x+(x+ d)/3 = 12

=> x=36/3=12

According to the question:

(x+d) = 2(x-d)

=> x=3d

Using x=12 from (i) we have d=4

Substituting the values-

(12+4) , 12 , (12-4)

16 , 12 , 8

Hence the smallest number is 8. OPTION (C)