Answer:
The average number of miles he traveled each day is 
Step-by-step explanation:
In <u>order to calculate the average</u>, we notice that it is a 3-day race, and we have the data of miles traveled each day. Mathematically we are saying that
![A=\frac{1}{3}[20t+15(t+6)+25(t-3)]](https://tex.z-dn.net/?f=A%3D%5Cfrac%7B1%7D%7B3%7D%5B20t%2B15%28t%2B6%29%2B25%28t-3%29%5D)
<em>where A is the average</em> we want to calculate, so

therefore

is the average number of miles he traveled each day, wich is the polynomial b.