Odd equation
 

It's not illogical, it's just wrong.

did you divide by zero anywhere in there?

Is that the whole equation? or did you bring us in halfway through?

If that's the whole equation, then your maths teacher has just pulled random numbers out of thin air and expected them to work (In other words, yes, you need a new teacher)

If it's only halfway through, then you may have gone wrong earlier on.

BTW, a maths teacher is not a proper maths teacher if they can count. However, the ability to perform simple and complex algebra is also a must.

What he said ^