Physics Pre-AP problems

I did some 6 of my problems but I'm kinda confused yawll. I need some help here are the problems.

12. In 1999, the Moroccan runner Hicahm El Guerrouj ran the 1-mi race in 3 min, 43.13 s. What was his average speed during the race in m/s?

18. A race car travels a complete lap on a circular track of radius 500 m in 50 s. (a) The average velocity of the race car is (1) zero, (2) 100 m/s, (3) 200 m/s, (4) none of the preceding. Why? (b) What is the average speed of the race car.

20. A student throws a ball vertically upward such that it travels 7.1 m to its maximum height. If the ball is caught at the initial height 2.4 s after being thrown (a) what is the ball's average speed, and (b) what is the average velocity?

24. A plot of position versus time is shown for an object in linear motion. (a) What are the average velocities for hte segments AB, BC, CD, DE, EF, FG, and BG? (b) State whether the motion in uniform or nonuiniform in each case. (c)What is the instantaneous velocity at point D?

30. Two runners approaching each other on a straight trach have constant speed of 4.50 m/s and 3.50 m/s, respectively, when they are 100 m apart. How long will it take for the runners to meet, and at what position will they meet if they maintain these speeds?

5. Discuss Positive Velocity with Positive and Negative Acceleration.

6. Discuss Negative Velocity with Positive and Negative Acceleration

9. Discuss Velocity sign conventions for free fall.

10. Discuss signs for free fall acceleration.

Please yawll help a brother out.