Answer:
Explanation:
It would help you if you drew charts of what is happening. The red tank is loosing volume. It's chart is on the left.
The blue tank is gaining water (the same amount as the red is loosing)
The red graph is the red tank.
The blue graph is the blue tank.
All you really have to understand is the the slopes (3 and - 3) and the same numerically and the rates are the same numerically. So the negative slope means loose. and the positive slope (blue) gains.
The graphs have to start somewhere. You can't make a graph like one without a starting point.
The blue container starts at 0,0. I think that's easy enough to understand. At the beginning of your experiment, the blue container is empty.
The red container starts (arbitrarily) at 3 (the y intercept). It is just a number. It means that the red container starts with 3 gallons.
Neither graph should go into a negative region. I don't know how to make desmos not go into a negative region. Just block them out in your mind. Everything should take place in quadrant 1 bound by the +x and + y axis.