Answer:
200 marbles
Explanation:
She starts with 400 marbles.
She gives away 2/4 of them
How many does she have left?
How can we simplify this?
Well, 2/4. It makes the problem seem longer and more complicated then it really is. 2/4 is the same as 1/2.
Now what's one half of 400?
200!
You could subtract the 200 from the 400 to officially see how much he has left, but knowing that 200 is half of 400, there will still be 200 left over.
If you ever need more help, don't be afraid to reach out! I hope this helps!