You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
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.

Context: Sam is 6 feet tall and Alex is 5 feet tall 

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

New input: Context: At the arcade Dave had won 18 tickets. If he used 5 to buy some toys and 11 more to buy some clothes 

 Question: How many tickets did Dave have left?
Solution:
2