The value of x can be calculated as,
[tex]\begin{gathered} \text{ summation of angles = 360}^{\circ} \\ 12x+90+(2x+5)+(17x-14)=\text{ 360}^{\circ} \\ 31x+95-14=360 \\ 31x=360-81 \\ 31x=279^{\circ} \\ x=\frac{279^{\circ}}{31} \\ x=9 \end{gathered}[/tex][tex]\begin{gathered} \text{mAD }=\text{ 12x} \\ =12\times9 \\ =108^{\circ} \end{gathered}[/tex][tex]\begin{gathered} \text{mBC}=(2x+5)^{\circ} \\ =(2\times9)+5 \\ =18+5 \\ =23^{\circ} \end{gathered}[/tex][tex]\begin{gathered} \text{mDC }=(17x-14)^{\circ} \\ =(17\times9)-14 \\ =153-14 \\ =139^{\circ} \end{gathered}[/tex][tex]\begin{gathered} \text{mDBC }=\text{ }(2x+5)^{\circ}+(17x-14^{})^{\circ} \\ =23^{\circ}+139^{\circ} \\ =162^{\circ} \end{gathered}[/tex]
