“If Johnny has 3 apples, and Jane takes 1 apple, how many apples does Johnny have?”
Depends.
Did Jane take an apple from the only source of apples stated in the question; Johnny? If so then 2.
Did Jane take one apple from a source not stated in the question. If so then 3.
Has Jonny eaten any of his apples? If so then |3-n| where n is the number of apples Johnny has eaten.