You are given a math word problem and you are supposed to only use subtraction on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

[Q]: Context: There are 20 different books in the ' crazy silly school ' series. If you are yet to read 5 of the books 

 Question: How many books have you already read?
[A]: 15


[Q]: Context: Mary is baking a cake. The recipe calls for 9 cups of sugar 7 cups of flour and 4 cups of salt. She already put in 2 cups of flour. 

 Question: How many more cups of flour than cups of salt does she need to add now?
[A]: 1


[Q]: Context: Baker made 54 cakes. He sold some of them. If he still has 13 cakes left 

 Question: How many cakes did baker sell?
[A]:
41