Question

A jug of water is 12 full. If 3 children equally share the water, what fraction of the full jug does each child get?

Answer 1

what does "12 full" even mean?

I suspect a typo, but hey, It's not my job to figure out what you mean.
It's your job to say it so clearly you cannot be misunderstood.

Answer 2

A jug of water is 1/2 full. If 3 children equally share the water, what fraction of the full jug does each child get?