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 
15.6 in 13 minutes? are you asking how it got to 15.6 in 13 minutes?
Answer: 50%
Step-by-step explanation:
In 2010, there were only 2 bike manufacturers and they had market shares of 30% and 70%.
A new manufacturer joins the market and captures 10% of the market share and Splendor increases to 40% of market share.
Market shares:
Yamaha = 10%
Splendor = 40%
Passion = 100% - 10% - 40%
= 50%