If the mom eats a 1/12 of the pot and then the brother also eats a 1/6 of the pot, then it is 9/12 left of pasta still. The reason for that is since 1/6 is equivalent to 2/12 so 1/12 plus 2/12 is 3/12, and if u subtract 3/12 from 12/12 it will give you 9/12 which can be simplified to 3/4 left of the pot.
