Since interior angles of a triangle adds up to 180 degrees, we can write:
![7x+(13x-3)+(8x+15)=180](https://img.qammunity.org/2023/formulas/mathematics/college/1g5aomk99an229hqaps57nj19k2oeekx66.png)
If we clear parenthesis and combine similar terms, we get
![7x+13x+8x-3+15=180](https://img.qammunity.org/2023/formulas/mathematics/college/kfi9qkk62k2np3z1i5fca6532xyp41418a.png)
which gives
![28x+12=180](https://img.qammunity.org/2023/formulas/mathematics/college/alp149cyaw2r8cou509vyl3aj2j5hmxut2.png)
If we move +12 to the right hand side as -12, we obtain
![\begin{gathered} 28x=180-12 \\ 28x=168 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/seuyljmi3zrtqyg5kkkwfl925sp69yb3n7.png)
then, x is equal to
![\begin{gathered} x=(168)/(28) \\ x=6 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/zrt6ts6133p28tu03lh316wls88ehi8i24.png)
Now, we can substitute this values into each angle
![\begin{gathered} \measuredangle A=7x\Rightarrow\measuredangle A=7(6)=42 \\ \measuredangle B=13x-3\Rightarrow\measuredangle B=13(6)-3=75 \\ \measuredangle C=8x+15\Rightarrow\measuredangle C=8(6)+15=63 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/8wmthc099jhkwoogoawkrchxhtghq4jg2e.png)
Therefore, the answers are
![\begin{gathered} \measuredangle A=42 \\ \measuredangle B=75 \\ \measuredangle C=63 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/qe7j9zisxux3x8kbsaey02crs0tbbajls7.png)