Answer :
1) The teacher may be reviewing a similar problem that may be on the quiz, if you pay attention you'll be able to understand how to solve it if you already don't.
2) The teacher may include a new concept that wasn't taught previously and may be showing how to solve it because she put it on the quiz, if you pay attention you'll know the new concept and be able to answer it on your quiz and if you didn't pay attention then you'll be confused because you'll be clueless on how to solve that equation.
3) The teacher may be showing a particular method that she wants the quiz written in and if you don't pay attention you may solve it in a different method and marks may be deducted from your answers.
2) The teacher may include a new concept that wasn't taught previously and may be showing how to solve it because she put it on the quiz, if you pay attention you'll know the new concept and be able to answer it on your quiz and if you didn't pay attention then you'll be confused because you'll be clueless on how to solve that equation.
3) The teacher may be showing a particular method that she wants the quiz written in and if you don't pay attention you may solve it in a different method and marks may be deducted from your answers.