How to take away from a variable? JAVA SCRIPT

Could someone tell me whats wrong with this?

Heres My Errors
Assets/Destroy.js(12,15): BCE0034: Expressions in statements must only be executed for their side-effects.
Assets/Destroy.js(15,8): BCE0046: 'is' can't be used with a value type ('int')
Heres My Code...How do i take away 5 from health everytime i click fire1?
#pragma strict

public var other : GameObject;
var Damage = 5;
var Health = 20;

function Update ()
{
if(Input.GetButtonDown("Fire1"))
{
Health - Damage;
}

if(Health === 0)
{
Destroy(other);
}

}

 

Try "Health = Health - Damage" instead.

And there should be only two equals signs for "is equal to" - but you should do "if (Health <= 0)" on the lower part.

 

Thanks so much! Works........Ive Been trying to learn code forever, this site is perfect !

 

No problem, good luck!