How am I supposed to answer this question if it doesn't tell me how many gallons the energy-saving showerhead uses compared to the regular one?

A standard showerhead in Jen's house dispenses 5 gallons of water per minute. Jen changed this showerhead to an energy-saving one. The equation shows the amount of water dispensed, y, as a function of the number of minutes, x, for the new showerhead.

y = 3x

How much water does Jen save each day with the change in showerheads if she uses the shower for 8 minutes each day?

16 gallons
17 gallons
32 gallons
37 gallons

First, you have to analyze what the function means. It tells you that x is the number of minutes in the shower, so now we have y=3(minutes in shower). Logically, 3 has to be gallons per minute so that the equation makes sense, since you're multiplying 3 by minutes in the shower. It also uses the same phrasing in the beginning of the problem when it says "A standard shower head in Jen's house dispenses 5 gallons of water per minute." Now, it's 3 gallons of water per minute (x). That means y has to be overall gallons. So, now the equations is overall gallons=3 gallons per minute. If she uses the shower for 8 minutes we can plug in for x. So now the equation is overall gallons=3 gallons times 8 minutes, or overall gallons=24 gallons. With the new shower head, 24 gallons is used. Now to find for the old shower head. 5 gallons per minute times 8 minutes = 40 gallons. Now we subtract to find out how many gallons Jen saves each day. 40-24=16. She saves 16 gallons.