if you want kids to learn math, make them play yugioh duel monsters
that card game as a lot of math in it

For smaller numbers (<100) the math is way too easy and you have to wait for the right ballon to come up. With the more difficult ones, you need longer to figure it out but still, need to wait if you made it. generally, the balloons always are at most +4 or -4 of the answer. this only works for addition or subtraction. if you have something like 18x18 it doesn't make sense. It would be better to have the ballons in intervals of 18. So in this case 290, 308, 324, 342, 360. Or make the balloons have the numbers where you get when you make a mistake in the calculation but that would need testing.
So I suggest making more ballons so you don't have to wait so long and a difficulty curve so you don't get something like 1x4 and 7-2 after you hat to do 18x18 which were what I got.