Question

Explain what it means for two variables to be directly related

Answer 1

It would be considered "like terms"
it is when there is two of the same variables, exponents.

Answer 2

It means that both variables are related in a way that one change in a variable, will result in a change in the other. 
There is Directly related and Inversely related. 
Directly is when one change happens to one variable, an equal change will happen to the other. 
Inversely is when one change happens to one variable, an opposite change will happen to the other.