C++ classes help...program written but i get linker errors?

Im working on a program that calculates speed when accelerating and braking but it uses classes... i need help here is my code so far

#include<iostream>

#include<cstring>

using namespace std;

class Car

{

private:

int yearModel;

string make;

int speed;

public:

void Car::setspeed(int);

void Car::setmake(string);

void Car::setyearModel(int);

int Car::getspeed() const;

string Car::getmake() const;

int Car::getyearModel() const;

int accelerate(int);

int brake(int);

};

int Car::getspeed() const

{

return speed;

}

string Car::getmake() const

{

return make;

}

int Car::getyearModel() const

{

return yearModel;

}

void Car::setspeed(int a)

{

speed = a;

}

void Car::setmake(string b)

{

make = b;

}

void Car::setyearModel(int c)

{

yearModel = c;

}

int accelerate(int num)

{

num += 5;

return speed;

}

int brake(int num)

{

num += 5;

return speed;

}

int main()

{

Car vehicle;

int x = 0, y = 0;

string name;

cout << "What is the initial speed? ";

cin >> x;

cout << "What is the make? ";

cin >> name;

cout << "What is the year the car was made? ";

cin >> y;

vehicle.setspeed( x );

vehicle.setmake( name );

vehicle.setyearModel( y );

cout << " The make of your car is " << vehicle.getmake() << endl;

cout << "Your car was built in " << vehicle.getyearModel() << endl;

cout << "The intial speed is " << vehicle.getspeed() << endl;

cout << "After the car has accelerated, the speed is " << vehicle.accelerate(x) << endl;

cout << "After the car has applied the brakes, the speed is " << vehicle.brake(x) << endl;

cout << "After the car has accelerated, the speed is " << vehicle.accelerate(x) << endl;

cout << "After the car has accelerated, the speed is " << vehicle.accelerate(x) << endl;

cout << "After the car has applied the brakes, the speed is " << vehicle.brake(x) << endl;

cout << "After the car has applied the brakes, the speed is " << vehicle.brake(x) << endl;

cout << "After the car has accelerated, the speed is " << vehicle.accelerate(x) << endl;

cout << "After the car has applied the brakes, the speed is " << vehicle.brake(x) << endl;

cout << "After the car has accelerated, the speed is " << vehicle.accelerate(x) << endl;

cout << "After the car has applied the brakes, the speed is " << vehicle.brake(x) << endl;

system ("PAUSE");

return 0;

}