Deducting percentage, calculate what percentage needs to be added to reverse

In the wb, a percentage is deducted from an original number, in this case 100.

So -20% = 80

I need to calculate what should be added percentage-wise to get back to 100, in the range from 1-30%

https://www.excelforum.com/attachmen...1&d=1552642087

Do you mean what percentage of the number in column C needs to be added to bring it back to 100?

If so the try this in D7 and copy down:
=(B7-C7)/C7

If not, give us a couple of manually generated expected results so we can better understand the requirement.

BSB