You need to remember that there are 360 degrees in a circle. Based on this, you can set up the following equation:
![mUR+mRS+mST+mTU=360\degree](https://img.qammunity.org/2023/formulas/mathematics/college/dzddfadksaozh86yclwhnwtl45aa5fpwig.png)
Knowing that:
![\begin{gathered} mUR=100\degree \\ mRS=9x+35\degree \\ mST=x+65\degree \\ mTS=15x+35\degree \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/l6zrf4z8uuykqyovqiml6hd3uyhc17d18k.png)
You can substitute the expressions into the equation and solve for "x":
![\begin{gathered} 100\degree+(9x+35\degree)+(x+65\degree)+(15x+35\degree)=360\degree \\ \\ 235\degree+25x=360\degree \\ 25x=360\degree-235\degree \\ 25x=125\degree \\ \\ x=(125\degree)/(25) \\ \\ x=5\degree \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4u39ecdcj5oprd0ebhm3cfdg7me3qoq0an.png)
Knowing the value of "x", you can find the measure of RS. This is:
![\begin{gathered} mRS=9x+35\degree \\ mRS=9(5\degree)+35\degree \\ mRS=45\degree+35\degree \\ mRS=80\degree \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/53k87jrm3boeixabdzipwuphz5hk3sp3nb.png)
The answer is:
![mRS=80\degree](https://img.qammunity.org/2023/formulas/mathematics/college/itxvj4k5icuywookx1cjrdj1hvlnbvoduv.png)