"multiplying 3 pounds 7 shillings and fourpence ha'penny by 13 pounds 3 shillings and fivepence ha'penny "

I can't imagine any circumstances where anybody would want to do that, and what the answer could possibly represent.

But when it comes to real calculations, the kind you might wan to do when adding up the cost of purchases a shop, £sd can actually be much easier to use, when you've grown up with it. It's a different way of thinking, but it works fine. That's assuming you are doing it in your head rather than writing it down or using a machine.