Question 203555
Let's do everything in terms of "thirds of a cup"


The original 2 cup mixture was one third flour.
Therefore the original mixture contained 2/3 of a cup of flour.


Like wise, the original mixture contained 4/3 of a cup of cornmeal.


Now we are adding three thirds (note how we express everything in thirds of a cup) of a cup of flour.


There are now THREE cups of mixed flour+cornmeal - or in other words there are NINE THIRDS of a cup.

Of those nine thirds, FIVE of them (the original 2 plus the extra 3) are made up of flour

So the fraction of the final mixture made up of flour is 5/9