哪位高人指点GMAT 考题？

你题目有漏吧？
When n liters of fuel was added to a tank that was already 1/3 full, the tank was filled to 7/9 of its capacity. In terms of n, what is the capacity of the tank, in liters?

when n litres of fuel is added
Now new capacity =(1/3)x +n=(7/9)x
n=(7/9)x-(1/3)x
n=x(7/9-1/3)
n=x(7-3/9)
n=x(4/9)
x=9n/4 is the answer hence D is the option