You are solving for the height. Use the formula:
c² - b² = a² in which c = hypotenuse
(13)² - (5)² = a²
Simplify
169 - 25 = a²
144 = a²
Isolate the a. Root both sides
√144 = √a²
a = √144
a = √(12 x 12)
a = 12
C) 12 feet is your answer
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It’s not exactly equal to one, but in many cases in math they ask for a rounded answer.
L1: 2x+4y-3=0 ..........(1)
P: (2,0)
The point on the line L1 closest to the given point P is at the intersection of L1 with L2, which is the perpendicular passing through P.
Slope of L1=-2/4=-1/2
Slope of L2=-1/(-1/2)=2
Since it passes throug P(2,0), we can use the point-slope formula:
(y-0)=2(x-2) =>
L2: 2x-y-4=0.............(2)
Solve for x & y using (1) and (2) to get intersection point required:
(1)-(2)
2x-2x + 4y-(-y) -3 -(-4) =0
5y=-1, y=-1/5
Substitute y=1/5 in equation (1)
2x+4(-1/5)-3=0 =>
2x-19/5=0
x=19/10
=> the point on L1 closest to (2,0) is (19/10, -1/5)
Your question is a little ambiguous, but I am assuming that you meant to say the function 
Thus, I am solving your question based on assuming the function such as

But, it would still clear your concept, no matter what the function is.
Answer:
we conclude that

The graph is also attached.
Step-by-step explanation:
Given the function

We know that the domain of a function is the set of input or argument values for which the function is real and defined.
As the function has no undefined points nor domain constraints.
Thus, the domain is

Therefore, we conclude that

The graph is also attached.
He had 40 pencils left after he gave away 8, so originally he had 40 + 8 pencils, which is 48.
Now, he bought 4 packages, which had a total of 48 pencils, so divide 48 by 4, which is 12. He had 12 pencils in each package.
To determine the solution arithmetically, first add 8 to 40, then divide 48 by 4.
To determine the solution algebraically, set up and solve the equation 40 = 4x - 8.
Each package contained 12 pencils.
Hope this helps