1) 5 different levels, 1 array for each level of difficulty.
2) Have a menu screen that would have the player choose the level of difficulty.
3) When they click the button, it changes a global value.
4) The global value then opens the desired array.
With what's given, this is my guess--
Thank you for posting this, you have helped me in so many ways on a project. "can i ask for a sample of math quiz game ?" That is a pretty big ask because that would pretty much develop the game for you. Can you take a screen shot or show the Capx file where you are stuck, or better define the problem that needs to be fixed.
@korbaach and Kyatric This is a solution to something I have been working on related to a dialogue I've been programming.