You are given a math word problem and you are supposed to apply an addition mathematical operator 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: Paul had some books. After selling 137 in a garage sale he had 105 left. 

 Question: How many books did he have at the start?

Answer: 242


Question: Context: For the walls of the house he would use 12 large planks of wood and 10 small planks. If large planks together need 15 pieces of nails to be secured and small planks together need 5 nails. 

 Question: How many nails does John need for the house wall?

Answer: 20


Question: Context: Winter is almost here and most animals are migrating to warmer countries. There are 3 bird families living near the mountain. 26 new bird families came to live near the mountain from the arctic while 2 bird families flew away further south for winter. 

 Question: How many bird families were left near the mountain?

Answer:
27