What are hidden questions and why are they important when solving multiple-step-problems?

In a nutshell, hidden questions are implied questions in a multiple step math problem. For example, if Apples were on sale for $6 per dozen and Mike bought two dozen Apples and paid with a $20, how much change does he get? The hidden question (or implied question) is how much did he spend on Apples? $6 x 2 = $12. Now you simply subtract $12 from $20 to get Mike's change of $8. But you needed to calculate the $12 first! That was the "hidden" question and it is important because you need the result to get your final answer.