I need to make sure i have all this down, math , acceleration?

Question

1. if an object travels for 15 min with a constant velocity of 12 miles per hour west ,what is the acceleration?

2.A sportcar goes from a velocity of 12 meters per second east in 2 seconds. what is the cars acceleration?

3. A train takes a long time to stop. thats what makes trains so dangerous to people who cross the tracks when one is near. if a train is traveling at 30 miles per hour south and takes 12 minutes to come to a stop what is the trains acceleration?

I have most of the equation written out I just want to make sure I am getting it all down.

Answer 1

Speed is change in distance over time.
Acceleration is change in speed over time

1. ..with CONSTANT velocity.... acceleration is zero.

2 ...from 12 metres per second... TO WHAT? Need more info here!

3. 30 mph = 0.5 miles per minute. Change in speed is -0.5 (negative means slowing down) divided by 12, or -1/24 miles per minute per minute.