Hello There!
To find the mean, add up all the numbers and divide according to how many numbers there are. The mean for this set would be <em>"9"</em>
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To find the median, place the numbers in value order and find the middle. if there is no middle, add up the two numbers in middle and divide by 2. In this set, the median would be <em>"8.5"</em>
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To find the mode or modal value, it is best to put the numbers in order. Then count how many of each number. A number that appears most often is the mode. In this set, there would be no mode.
The range of a set of data is the difference between the highest and lowest values in the set. In this set, the range would be <em>"12"</em>
To do this problem, you gotta cross-multiply. SO,

multiplied by

12 times 14 = 168
21 times 3 = 63
Then the final answer is
Here I copy the steps and indicate where the error is.
Square root of negative 2x plus 1 − 3 = x=> <span>this is the starting equation
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√[ - 2x + 1] - 3 = x
Square root of negative 2x plus 1 − 3 + 3 = x + 3 in this step she added 3 to each side, which is fine
<span> Square root
of negative 2x plus 1 = x + 3 <span>she made the addtions => fine</span></span>
Square root of negative 2x plus 1 − 1 = x + 3 – 1 due to <span>plus 1 in inside the square root, this step will not help</span>
<span> Square root
of negative 2 x = x + 2 <span>wrong! she cannot simplify - 1 that is out of the square root with +1 that is inside the square root
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<span>Then, from here on all is wrong, but she made other additional mistakes.</span>
(Square root of negative 2 x)2 = (x − 4)2 −2x <span> the right side should be (x+2)^2 which is x^2 + 4x +4 not (x-4)^2 - 2x</span>
Later she made a mistake changing the sign of -8x to +8x
Those are the mistakes. Finally, the global error is that she should verify whether the found values satisfied the original equation.
I believe it is 180° around H and translate 2 up 5 right