i may not know much about coding yet, but i think this is a VERY possible thing to do with the "random" command, i think somthing along the lines of making every set of math problems a function, or somthing like it, and giving each function a sort of "call number" saying "hey math problem set 1, youre up this round." and then finding a way to randomize which number is picked each time the game starts. i also commend your efforts to bring gaming to an exeptionally good cause.
....well theres my 2 cents