a)  What is the average velocity from $0$ to $10\ \mathrm{seconds}$?

$v_{avg}=50\ \mathrm{\displaystyle \frac{m}{s}}$

To find the average velocity, use:

a) $$v_{avg}=\frac{\Delta x}{\Delta t}$$

$$v_{avg}=\frac{(500-0)}{(10-0)}$$

$$v_{avg}=50\ \mathrm{\displaystyle \frac{m}{s}}$$

b) What is the average velocity from $10$ to $20\ \mathrm{seconds}$?

$v_{avg}=150\ \mathrm{\displaystyle \frac{m}{s}}$

b) $$v_{avg}=\frac{\Delta x}{\Delta t}$$

$$v_{avg}=\frac{(2,000-500)}{(20-10)}$$

$$v_{avg}=150\ \mathrm{\displaystyle \frac{m}{s}}$$

c)  What is the average velocity from $0$ to $20\ \mathrm{seconds}$?

$v_{avg}=100\ \mathrm{\displaystyle \frac{m}{s}}$

c) $$v_{avg}=\frac{\Delta x}{\Delta t}$$

$$v_{avg}=\frac{(2,000-0)}{(20-0)}$$

$$v_{avg}=100\ \mathrm{\displaystyle \frac{m}{s}}$$