how do i make a variable stay at a number?

How do i make a variable not get past a number?
i ahve this script that should make a car accelerate, when i press “w” a variable will go from 0 and up. But there is a limit speed, and how do i make that?
so the variable want go further up that for example 20.?

Here is the script:

#pragma strict

var spin = 3;

var speed : float = 0.0;

function Update ()
{

if(Input.GetButton(“FORWARD”)
{

speed = speed+0.2;

transform.Translate(Vector3(0,0,speed) * Time.deltaTime);

}

}

#pragma strict

var spin = 3;

var speed : float = 0.0;

function Update () {



if(Input.GetButton("FORWARD") {

speed = speed+0.2;

if(speed>=20){
	speed = 20;
}

transform.Translate(Vector3(0,0,speed) * Time.deltaTime);

}

}

The simplest way:

if(speed > 20) { speed = 20; }