Answer:
The side length of of the base of the tank is 15 inches.
Step-by-step explanation:
We are given the following in the question:
Cost of the tank and filter system = $280
Perimeter of tank base = 60 inches
The perimeter of tank is in the shape of square.
We have to find the side length of the base of the tank.
Perimeter of tank base = Perimeter of square =

Thus, the side length of of the base of the tank is 15 inches.