Answer:
5.66 inches
Step-by-step explanation:

a² + 7² = 9²
a² + 49 = 81
a² + 49 - 49 = 81 - 49
a² = 32
a = square root of 32
a = 5.6568 or 5.66 inches
I used the Pythagorean Theorem to solve this.
Answer:

If we divide both sides by
we got:

And we can use the normal distribution table or excel to find the probabilites and we got:
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the area of a population, and for this case we know the distribution for X is given by:
Where
and 
We select a a sample of n =4 and since the distribution for X is normal then we know that the distribution for the sample mean
is given by:

And we want to find this probability:

If we divide both sides by
we got:

And we can use the normal distribution table or excel to find the probabilites and we got:

Answer:
Step-by-step explanation:
√a+√b=√(a+b)
squaring
a+b+2√a√b=a+b
or 2√a√b=0
which is possible only if a=0 or b=0
Both a and b can't be zero as a≠b
29.87 should be it hopefully