Ignore the more complicated fraction. All they care about is finding the LCD of y and (y-3)/3
Think of the first y as y/1. We can write this as 3y/3 (multiply top and bottom by 3)
So y + (y-3)/3 turns into 3y/3 + (y-3)/3. At this point we can combine the fractions since the denominators are both 3.
Final Answer: Choice D) 3