Motivation is an important factor in learning. I don't disagree that it is necessary to learn how to simplify an equation such as your example above. HOWEVER, there is nothing wrong with letting kids in on "why solving the equation you mention above might be helpful in the future. Nobody likes to be kept completely in the dark about why they need to learn certain things, if not, they stop studying and address custom writing to write homework for them.
Motivation is an important factor in learning. I don't disagree that it is necessary to learn how to simplify an equation such as your example above. HOWEVER, there is nothing wrong with letting kids in on "why solving the equation you mention above might be helpful in the future. Nobody likes to be kept completely in the dark about why they need to learn certain things, if not, they stop studying and address custom writing to write homework for them.