First u need to make the denominator same for 2/5 n 1/3 because what he hv first n what he hv at the end. Then dont get confused w the units. Do the keychain first and find out how many keychains he have left. So 2/15 of the keychains were left. Then find out how many units left for bookmarks then find out how many units he sold. Hope it helps. I know its a bit confusing. But better to draw models