D.6 is your answer
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1. The major arc ED has measure 180 degrees since ED is a diameter of the circle. The measure of arc EF is
, so the measure of arc DF is

The inscribed angle theorem tells us that the central angle subtended by arc DF,
, has a measure of twice the measure of the inscribed angle DEF (which is the same angle OEF) so

so the measure of arc DF is also 64 degrees. So we have

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2. Arc FE and angle EOF have the same measure, 56 degrees. By the inscribed angle theorem,

Triangle DEF is isosceles because FD and ED have the same length, so angles EFD and DEF are congruent. Also, the sum of the interior angles of any triangle is 180 degrees. It follows that

Triangle OFE is also isosceles, so angles EFO and FEO are congruent. So we have

The first equation given 
We have to add 1 and 5 to the right side first. We will get,

To get rid of 6 from the right side we have to subtract 6 from both sides.



To find n we have to move -2 to the other side by dividing both side by -2.



So we have got the required answer for the first question.
The solution is n = 0.
The second equation given,

First we have to move 7x to the left side by subtracting it from both sides.



Now we have to move -2 to the right side by adding 2 to both sides.



We have got the required answer for the second question.
The solution is x = -7.
The third equation given,

We have to get rid of that negative sign from both sides. As we have negative sign to both sides we can cancel it out. We will get,

Now we have to move 4 to left side by subtracting it from both sides.




So we have got the required answer .
The solution is x = 4.
Answer:
B
Step-by-step explanation:
Answer:
DC = 3
Step-by-step explanation:
Based on triangle similarity theorem, we would have the following equation:

Plug in the values



Cross multiply
3(9 + DC) = 9×4
27 + 3DC = 36
Subtract 27 from each side
3DC = 36 - 27
3DC = 9
Divide both sides by 3
DC = 9/3
DC = 3