The number of volunteers that donated can be expressed as 32-n. To determine the total amount of milliliters each person donated, we can multiply 32-n by 470.
470(32-n)
This can be simplified using the distributive property.
470(32)-470(n)
=15040-470n
Both of the expressions, 470(32-n) and 15040-470n, are correct, although, you can use the one you prefer.