we know that
The measurement of <u>the external angle</u> is the semi-difference of the arcs it includes.
In this problem
![21\°=\frac{1}{2}[arc\ RU-arc\ SU]](https://tex.z-dn.net/?f=21%5C%C2%B0%3D%5Cfrac%7B1%7D%7B2%7D%5Barc%5C%20RU-arc%5C%20SU%5D)
Solve for the measure of arc SU
![42\°=[arc\ RU-arc\ SU]](https://tex.z-dn.net/?f=42%5C%C2%B0%3D%5Barc%5C%20RU-arc%5C%20SU%5D)


therefore
the answer is
The measure of the arc SU is 
3/18 = 1/6 =.16666666.....
.16(repeating)
your choice A and D are the same
and choice B and C are the same
Answer:
26
Step-by-step explanation:
Distance between (-2,5) and (-2,1) is 5
Distance between (-2,5) and (6,5) is 8
Distance between (6,5) and (6,1) is 5
Distance between (6,1) and (-2,1) is 8
5+8+5+8=26
Because his first string was tied up at the moment