They start with the numbers u need to know in order to slove the problem and there has to be a story behind it
Convection currents in the mantle are what causes the movement of tectonic plates. As the extremely hot molten material from the mantle rises toward the crust, it cools enough to become denser and sink back into the hotter area of the mantle.
Answer:
The answer is subdivided,created or destroyed
The focal length, like you said it's the distance between the FOCAL point and the mirror.
Hope this helps.... :)
