Lets assume, Sally has X pound of potatoes in her pantry.
So, 4/3 of the potatoes Sally has in her pantry =

Now, Sally needs 2/3 pound of potatoes and this 2/3 pound of potatoes is 1/3 pound more than that

So the representing equation will be:
(subtracting
from both sides)

(multiplying both sides by 3)
So, Sally has
pound of potatoes in her pantry.