sorry, try this
Code:
{if $product.list_price gt 0}
{math equation="100-(price/lprice)*100" price=$product.price lprice=$product.list_price format="%d" assign=discount}
<font class=MarketPrice>{$lng.lbl_market_price}: <s>
{include file="currency.tpl" value=$product.list_price}
</s></font>
{/if}