Given the task definition and input, reply with output. 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: Winter is almost here and most animals are migrating to warmer countries. There are 85 bird families living near the mountain. If 23 bird families flew away to africa and 37 bird families flew away to asia 

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

25