Imagine a physics person just asked you what your speed is while riding your bicycle on a flat road.  You say, "about 25miles per hour."

What does the physics person hear?  They hear your answer more like this...
"For each hour that passes, you move a distance of 25 miles."

There is a way to say this mathematically...

SPEED EQUALS DISTANCE OVER TIME, or S=D/T

This is no shocker, but what if you already know a speed and a distance, and need to find the time it would take for the motion to occur?
Maybe you are riding to the store 10 miles away and you have half an hour to get there.  Can you do it if you ride at your speed of 25 miles per hour?

Well, if one hour moves you 25 miles, then one half hour would get you 12.5 miles.  So the answer is yes!

To answer that question, we had to plug two numbers into the equation S=D/T.
25=10/T... do a little algebra to get "T" by itself.... T=D/S=10/25=.4hour

Since you had 50% of an hour and only needed 40%, you made it.

Seems like a lot of work to answer a simple question.  The equation is just a tool for us to use that makes things easier for us, especially when things get tougher.