Answer:
Independent Variable- size of aquariums
Dependent variable - number of surviving fish
Controls: nil
Step-by-step explanation:
In every experiment, the independent variable is manipulated and its effect on the dependent variable is observed as certain factors are kept constant.
In this study, the independent variable is the size of the aquariums. As this factor is manipulated, the number of surviving fish (dependent variable) changed accordingly. There was no mention of a control group in the experiment.
However, temperature, amount of food and type of food were held constant for all the experimental groups.
We want to find the axis of symmetry of the function;

STEP 1:
The equation for the axis of symmetry of a line is given as;

From the equation, a = 6 and b = -3, so,
STEP 2: Insert the values of a and b into the equation to obtain;

CONCLUSION:
Therefore, we see that the axis of symmetry is the line;
The graph is shown in the attached image.
They removed 4.5 tons in eight