We can use the is/of=p/100 method for this problem. Since it's 15% off, this would mean that the bill is 85% of what it was initially. Plug the values into the is/of=p/100 formula.
36.72/x = 85/100
Solve for x.
x=36.72/0.85
x=43.2
So, the bill was $43.20 before applying the voucher discount of 15% off.
You can calculate this by taking 36.72 and dividing it by 0.15 (15%). You would do this because it is the opposite of multiplying an original number by 0.15 (15%) to get 36.72.
