\(\color{red}\frac{13}{sin120}=\frac{7}{sinC}\)
\(\color{lime}13sinC=7sin120\)
\(\color{blue}sinC=\frac{7sin120}{13}\)
\(\color{purple}C= asin (\frac{7sin120}{13})\)
It doesn't look like a rainbow in this color pattern...... Never mind. C approximately equals 27.79 degrees.