Answer:
45.
Step-by-step explanation:
Since Hideki is draining a 45 gallon aquarium at a rate of 15 gallons per minute, to determine what is the initial value of the linear function that represents the situation, the following calculation must be performed:
45 (starting number) - 15(number of gallons per minute) X(minutes) = Y
Therefore, the equation would be 45 - 15X = Y, with which the initial value of the linear function that represents the situation is 45.