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.
Step-by-step explanation:

Answer:
or
Step-by-step explanation:
Given the following expression:

You can follow these steps in order to simplify it:
1. You need to apply Distributive property:

2. And now you must add the like terms. Then:

Therefore you get the following answer:
or