What makes a magnifying class and a mirror similar? What makes them different? (in a physics way, not their functions)

Awoman stands a distance d from a loud motor that emits sound uniformly in all directions. the sound intensity at her position is an uncomfortable 2.0×10-3 w/m2. at a distance 2.6 times as far from the motor, what are (a) the sound intensity and (b) the sound intensity level relative to the threshold of hearing?

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body

Need only answer if you think you know it