I'm sorry to sound like a complete idiot. I was doing it in discounts and now tried in calculations. This is what the code ended up looking like.
$this->Bookdiscounttenpercent = abs($this->Quantity >= 10 && $this->Quantity < 30 && $this->ItemType == 2) *( $this->TotalPrice * .10);
Am I suppose to do more with it? I'm not seeing the discount. Thanks.