at 7am a sewage treatment tank contains 3000000 gallons of water. starting at 7am, x gallons per minute flow into the tank, and y gallons per minute flow out of the tank. no water enters or leaves the tank otherwise. which of the following functions f models the number of gallons of water in the sewage treatment plant at 8am?

You’re not providing me with the choices, so all I can say is that you want something that contains:

- 3,000,000
- +60
*x* - –60
*y*

The 3,000,000 you need because that’s the starting value at 7am. The 60s you need because you’re given rates in gallons per *minute* and there are 60 minutes between 7am and 8am.

Hope that helps.