Okay, I've just had a quick look at Freaking Math, it's pretty easy to pull off, here's the psuedo.
You're going to want a text that shows an equation, let's set it out like this:
"random(0,50) + random (0,50) ="
And a second text object that shows an answer that's either right or close to it:
"equation.sum+random(-5,5)"
And finally two buttons, a tick and cross.
If the user hits the tick, compare the answer with the equation sum, if it's equal +1 to score. If they hit the cross invert the check. An incorrect answer resets the score to zero. Either answer causes the event to loop so you get a new question.
This was all typed out in a hurry, please ask if you have any questions/ feel free to correct any errors!