The question you opened
Five cookies and you take three
There are 5 cookies on the plate and you take 3 of them.
How many cookies do you have?
Three
You took three, so three are yours. The question follows the cookies in your hands, and nothing was eaten.
There are five cookies on a plate and you take three. How many do you have. Three. Most people say two, and the reason is worth looking at, because it happens to grown ups just as often as to children. As soon as two numbers appear in a sentence, a subtraction starts running in the background. Five take away three is two, and the answer arrives before anyone has checked what was being counted.
Two is a real number in this story. It is the number of cookies still sitting on the plate. If the question had asked how many cookies are left, two would be correct. The question asked about you, and you are holding three. So the skill here is reading rather than arithmetic. Before working anything out, say who or what the question is about. The plate, or your hands. Once you have said it, the answer is usually already there.
You can try the same trick on a friend with a small change and watch it work again. There are eight sweets in a bowl and you take four. Now the two answers happen to match, and nobody notices anything strange. Go back to five and three and the gap opens up again. A useful way to test yourself on any word problem is to answer with a full sentence rather than a number. I have three cookies. Two cookies are on the plate.
Full sentences force you to name the thing you counted, and a number on its own hides that. There is also a small joke buried in the question. Nothing says you ate anything, so the cookies are still cookies and everyone can have them back. The puzzle is about counting, and the plate is only there to give the subtraction something to grab. Heron falls for this one about half the time, usually while thinking about the cookies rather than the question.
Technique: Notice who the question is about