Answer: Choice A
The second fraction should not have been multiplied by 9
This is because 1/9 already has the LCD in the denominator. LCD stands for lowest common denominator.
The first fraction 2/3 does not have 9 in the denominator, which is why they multiplied top and bottom by 3
2/3 = (2*3)/(3*3) = 6/9
After each fraction has the same denominator (9), you can add the numerators to place over the LCD like so
6/9 + 1/9 = (6+1)/9 = 7/9
This means,
2/3 + 1/9 = 6/9+1/9 = 7/9