The only 'word story' I can think of reads like this:
"Once upon a time there was a teacher who didn't proofread her worksheets properly. That made her pupils very confused, it made their parents very angry and it made the teacher look very silly"
Unless maths has changed considerably since I got my degree in it (and taught it to A-level) the question is clearly meaningless. Even if it was numerically correct it should say 'sum' and not 'number' but, as it stands, it's nothing but twaddle.