Answer for 13 with explanation and steps shows (btw the container is filled 2/12th's)

If the container is divided into 12ths you should make that your common denominator.

So 1/4 now equals 3/12

Since we want this 3/12 to be empty we must subtract it from 12/12 leaving us with 9/12.

When we subtract 2/12 from 9/12 to get the amount that was already filled we get 7/12 which is the amount that needs to be filled.

To check we add our parts 2/12 and 7/12 to get 9/12 which is 3/4 of the container filled leaving 3/12 or 1/4 of the container empty.

Hope this helps ☺

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