Pre-decimal Calculation

Earlier this year, when I was researching an ancestor of mine in the National Records of Scotland archives in Edinburgh, I came upon this scrap of paper. It was wrapped in a small package of sundry church paperwork dating from the 1930s, tied up with a ribbon. The calculations are in pre-decimal pounds, shillings & pennies. I can't work out what's being done but there's conversion to & from pence with long division in tiny ink numbers. Maybe we should resurrect £ s/d.