Answer:
D. 914 feet
Step-by-step explanation:
We are given the distance that a person can see on a clear day from the upper observation platform of the Eiffel tower in Paris. We are then required to estimate the height of the upper observation platform using the formula;

Where d is the distance and h the height of the upper observation platform. The first step would be to solve for h, that is make h the subject of the formula in the above equation;
We multiply both sides of the equation by the reciprocal of 5/6 which is 6/5;

The next step is to eliminate the square root on the Left Hand Side of the equation by squaring both sides;

Given d is 25.2, h becomes;

To the nearest whole number, h becomes 914
The domain of a function is the set of values for which the function is defined; i.e. the function outputs a value for an input from the domain. That means that we must be able to plug in numbers for x and get numbers from y.
We can't take the square root of negative numbers (ignoring imaginary numbers), so that means we can take the square root of any non-negative number; i.e. we can take the square root of zero, and any positive number.
Therefore, any function that can take in values of x that are zero or more than zero has the same domain as the given function. So

is a function that has the same domain as

.
That is the difference of two squares and is factored in this way:
(7 +x) * (7 -x)
The mean will be 12. To find the mean, add all values and divide by the number of values. 5+19=24, 24/2=12