Consider this option:
1. using the property of the inscribed quadrilateral it is possible to make up the system of linear equations:
2.
[tex] \left \{ {{A+C=180} \atop {B+D=180}} \right. \ =\ \textgreater \ \ \left \{ {{2x+3+C=180} \atop {3x+9+2x-4=180}} \right. \ =\ \textgreater \ \ \left \{ {{C=107} \atop {x=35}} \right. [/tex]
answer: 107°
