You are expected to know that:

position function

velocity function

acceleration function

Given:

The average velocity is given by the slope of the secant line connecting the two points.

- Find the average velocity on the interval [1,3]

Thus,

Can you take it from there?

We simply evaluate v(3), that is, the velocity function when t = 3. I found that for you above

- Find the instantaneous velocity when t = 3

Can you take it from there?

s(t) gives the position function. we want the time when the position is zero, therefore, we set s(t) = 0 and solve for t, this will give you the required time. To be more explicit, we want t such that:

- How long does it take for the coin to hit the ground?

Can you take it from here?

For this question, we simply plug in the value of t we found in the previous question into the velocity function

- Find the velocity of the coin when it hits the ground.

Can you take it from here?