Mary is baking a cake. The recipe calls for 13 cups of flour and 49 cups of sugar. She already put in 38 cups of flour. How many more cups of sugar than cups of flour does she need to add now?
First, we need to figure out how many cups of flour Mary has left to add. We know that she's already added 38 cups of flour, and the recipe calls for 13 cups of flour in total. So we can say that

13 cups of flour - 38 cups of flour = -25 cups of flour

In other words, Mary has used up 25 cups of flour, and she has -25 cups of flour left to add. 

Next, we need to figure out how many cups of sugar Mary has left to add. We know that the recipe calls for 49 cups of sugar in total. So we can say that

49 cups of sugar - 25 cups of flour = 24 cups of sugar

In other words, Mary has used up 25 cups of flour, and she has 24 cups of sugar left to add. 

So Mary needs to add 24 cups of sugar and -25 cups of flour.