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.
One example: Context: Sam is 6 feet tall and Alex is 5 feet tall 

 Question: By how many feet is Sam taller than Alex? 
Solution is here: 1
Explanation:  Sam's height - Alex's height = 6-5 = 1

Now, solve this: Context: For Gwen's birthday she received 7 dollars. She spent some money and has 5 dollars left with her. 

 Question: How much money did she spend?
Solution:
2