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.
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Question: Context: Every day Ryan spends 6 hours on learning english and 2 hours on learning chinese.

Question: How many more hours does he spend on learning english than he does on learning chinese?

Answer: 4

Question: Context: Last week Fred had 78 dollars and Jason had 31 dollars. Jason delivered newspapers and now has 57 dollars. Fred washed cars over the weekend and now has 90 dollars.

Question: How much money did Jason earn by delivering newspapers?

Answer: 26

Question: Context: Carol was sending out birthday invitations to her friends. Each package of invitations she bought had 3 invitations in it and she bought 2 packs. If she wants to invite 9 friends

Question: How many extra invitations will she need to buy?

Answer:
3