Answer:
a) 
Now we can replace the velocity for t=1.75 s

For t = 3.0 s we have:

b) 
And we can find the positions for the two times required like this:
And now we can replace and we got:

Explanation:
The particle position is given by:

Part a
In order to find the velocity we need to take the first derivate for the position function like this:

Now we can replace the velocity for t=1.75 s

For t = 3.0 s we have:

Part b
For this case we can find the average velocity with the following formula:

And we can find the positions for the two times required like this:
And now we can replace and we got:

1 io is a moon not a planet.
2)C,The Milky Way is a spiral galaxy
3)D,this is called the particle wave duality,stuff can act like particles and waves at the same time.
4)the white dwarfs
5)using distance and compass direction(I’m not sure about this one though)
B)
The speed of the cart changed because it stopped.
Hope I could help!
-Marshy
Explanation:
Below is an attachment containing the solution.
The distance covered by Arthur is
3t
The distance covered by Betty from where Arthur started is
100 - 2t
They meet each other when this distance is equal
3t = 100 - 2t
t = 20 s
Since the dog has a constant speed of 5m/s, the distance that Spot has run is
5 m/s (20s) = 100 m