Two angles are labelled as supplementary angles when they both add up to 180 degrees.
The two angles given are S and T, and they are in the ratio 7 : 3.
This can be expresed as follows;
![\begin{gathered} \angle S\colon\angle T=7\colon3 \\ \angle S=(7)/(10) \\ \angle T=(3)/(10) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/pndx74whckbtzu20bxanhu9ggaqngu74rz.png)
Having been told that they both add up to 180 degrees, we now have the following;
![\begin{gathered} \angle S=(7)/(10)*180 \\ \angle S=126 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/iomsbjpzxux7hbu5p793n9u0tg2iaaunw3.png)
Similarly;
![\begin{gathered} \angle T=(3)/(10)*180 \\ \angle T=54 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/uhjwz3tsnqb6eeoyop7tezyamhvw57b65x.png)
ANSWER:
The angle measure of S is;
![\angle S=126](https://img.qammunity.org/2023/formulas/mathematics/college/xv0v5kglz9c72jn6mt836awdlkqc6jaoey.png)