Add full price to invoice

Hi,

I am trying to add the full price with a strike-through next to the discounted price on the invoice.
I tried to add the following to print-content.php but i just get 2 same prices, one with strike-through and one without, both are the same discounted price:
<span style=”text-decoration: line-through;”><?php echo wc_price( $product->get_price() ); ?></span><br>

Can you please tell me the right code to add?
Many thanks for you’re great plugin.