Answer:
The required equation is 
Step-by-step explanation:
Consider the provided information.
Student on the cross-country team runs 30 minutes a day as a part of her training,
30 minutes = 0.5 hours
As we know 
Let the distance she runs in miles, is represented by D, and her running speed, in miles per hour is represented by S.
Therefore, the required equation is: 
Part (A) At a constant speed of 4 miles per hour for the entire 30 minutes.
Substitute S=4 in above equation.



Hence, the required equation is 