To model the total amount of water, \( w \), that Martina used, you multiply the amount of water in each container by the number of containers.
Given that she used 8.5 ounces of water in each of the 5 containers, the equation can be completed as follows:
\[ w = 8.5 \times 5 \]
So the equation can be expressed in the form:
\[ w/1 = 8.5 \times 5 \]
Or alternatively:
\[ w/5 = 8.5 \]
You can choose either form based on your preference.