Apparently the equation "5 + 4 = ?" is not the same as "? + ? = 9"
For the 1st equation, you can only have 1 answer, but for the 2nd equation you can help unlimited combinations.
This also applies in real life.
Imagine that 5 and 4 are instructions given to you by the boss. If you follow them strictly, you'll get what the boss wants, but it'll be very mundane and boring because there is only one way to do it.
But for the second one, imagine that the boss tells you that there is something that needs to be achieved, but he doesn't tell you how it should be done. Instead, it is up to your own creativity and imagination to get to the final product.
Toyota uses the second equation. Reports say that if an employee follows exactly what the boss said, he'll be reprimanded for following it too strictly, and not adding his own creativity or imagination in the process.
Which equation would you like?
Extra: OMG, I dozed off at my desk for 30 minutes!