Mary is baking a cake. The recipe calls for 11 cups of flour and 40 cups of sugar. She already put in 8 cups of flour. How many more cups of sugar than cups of flour does she need to add now?
Mary has already put in 8 cups of flour. This leaves 3 cups of flour to add. 
The recipe calls for 11 cups of flour and 40 cups of sugar. 
We know that for every 1 cup of flour, we need 4 cups of sugar. 
Therefore, for 3 cups of flour, we need 3 x 4 = 12 cups of sugar. 
Mary has already put in 8 cups of sugar. This leaves 4 cups of sugar to add. 

Therefore, Mary needs to add 4 more cups of sugar than she does flour.