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.

Let me give you an example: Context: 21 children were riding on the bus. At the bus stop 5 children got off the bus while some more got on the bus. Then there were 16 children altogether on the bus. 

 Question: How many children got on the bus at the bus stop?
The answer to this example can be: 0
Here is why: Number of children who got on -> 21 - 5 + x = 16 , x = 0, hence no one got onto the bus

OK. solve this:
Context: Rachel picked 6 ripe apples from her tree. Now the tree has 2 ripe apples and 4 unripe apples. 

 Question: How many apples did the tree have to begin with?
Answer:
12