Nice :D
I remember to have made a magick like this in scool, and it worked quite nice...
so does this one, but i would sugest that you put in the formula for what to do after you have picked youre number and added the 2 numbers together, then in stead of writing fx. 52 minus 7 try writing in the formula fx 52 - 7 instead, i didnt get it right away because of that... but this is sure good work :D