You just have to change the button to - in our formula. Cell C2 contains the number 20 equal to the 02 value. Go to Format Number Percent in Google Sheets menu to apply the percentage view.
An alternative but more long-winded calculation would be to calculate 10 of the number and then subtract it from the original number with one of these formulas.
Instruction on percentage calculator operation. A2-A2B2 15 of 120 is 18. Divide the percentage number by 100 to convert to a decimal. Go to Format Number Percent in Google Sheets menu to apply the percentage view.