If you think about it based on the grammar, the answer could also be actually six
so, Sally has 4 apples
she goes to the store and takes 2 away from the store, buys them, and adds them actually, assuming she didn't eat any apples, give some to friends, throw away, etc.
So she adds those two apples to her collection, and 4+2=6
so the REAL answer to this question is: NEI (Not Enough Information)
She never left anywhere to get apples, so the answer is 4. She took 2 away from herself and added it to her own hand. 2+4-2=4