1. Set t=0 when the driver applies the brakes. You should be able to write an equation for the speed of the car from t=0 until it stops. Then you integrate to get the distance traveled.
2. You integrate the velocity to get an equation for position, and use 8cm to evaluate the constant of integration. Then you solve to find the time when it's at O. Then you differentiate the velocity to get the acceleration as a function of time and evaluate it at the time you calculated.
3. Here you need the acceleration due to gravity. You can write an equation for the velocity as a function of time, then integrate to get position as a function of time, then set it to 553 to get the time when it hits the ground. Then you plug in to your equation for velocity.
That's an overview of the process - if you're having trouble with a specific step, post again and we'll help you through it.