Final answer:
The equation that represents the relationship between the gallons of water in the tank and the minutes the tank has been draining is x = 450 - 20y, and the correct answer is option B.
Step-by-step explanation:
The student asked to write the equation that represents the relationship between the gallons of water in the tank (x) and the minutes the tank has been draining (y). Given that the tank starts with 450 gallons and is draining at a rate of 20 gallons per minute, we can write this relationship as:
x = 450 - 20y
This means for every passing minute (y), 20 gallons are subtracted from the initial 450 gallons. On the other hand, y can be expressed as:
y = \frac{x}{20}
However, this y equation is not one of the choices presented. The correct answer from the choices provided, which matches the given relationship, is option B: x = 450 - 20y, y = 20x.