Mary is baking a cake. The recipe calls for 33 cups of sugar and 44 cups of flour. She already put in 20 cups of sugar. How many more cups of sugar does she need to add?
1. Mary is baking a cake. 
2. The recipe calls for 33 cups of sugar and 44 cups of flour. 
3. She already put in 20 cups of sugar. 
4. How many more cups of sugar does she need to add?

To solve this problem, we need to find out how many cups of sugar are left. We can do this by subtracting 20 cups (the amount of sugar she has already put in) from 33 cups (the total amount of sugar the recipe calls for). 

33 cups - 20 cups = 13 cups 

Therefore, Mary needs to add 13 more cups of sugar to the cake.