Complex sentence: The debt increased the already outstanding debt from the Seven Years' War Taxes on the British population increased over the years and duties on some items were also added, the average tax for the British public being four shillings in every pound.
Split into simpler sentences: The debt increased the already outstanding debt from the Seven Years' War Taxes on the British population increased over the years and duties on some items were also added. The average tax for the British public was four shillings in every pound.