A person who takes a 10-minute shower might use between 20 and 25 gallons of water, depending on the speed of the water passing through the showerhead . The lower the speed, the less water that is used. The equation w=2.5m models the amount of water, w, in gallons that passes through a showerhead in minutes.

Which is the independent variable and which is the dependent variable?

The amount of water in gallons, w, is the independent or dependent variable.

The time in minutes, m, is the independent or dependent variable.