Finding a percentage difference of 2 values

HI

This seems simple ,but the formulas I have found on net dont seem to look correct.

I get raw data each week and I turn those numbers into a percentage

For example

I need a formula to calculate and display the percentage difference of column F and Column N.
It should show if the column F went up in percentage or if it went down.

so last week was 10.8% this week was 7.7% . Show the difference in percentage. The percentage went down so its -3.1%

How do I display this?

I ve attacheda photo help better assist in the answer.ATT00001.gif
Thanks in adavance

The raw is fine. I over complicated the situation. Thanks.