$\begin{align}  & \angle EFB+\angle BFG={{180}^{\circ }}\text{  }\!\!\{\!\!\text{ sum of angles on a straight line }\!\!\}\!\!\text{ } \\ & \text{10}{{\text{0}}^{\circ }}+\angle BFG={{180}^{\circ }} \\ & \angle BFG={{80}^{\circ }} \\ & \angle FBG+\angle BFG=\angle BGH\text{    }\!\!\{\!\!\text{ Sum of two opp}\text{. angles of a }\vartriangle \} \\ & {{80}^{\circ }}+{{40}^{\circ }}=\angle BGH \\ & \angle BGH={{120}^{\circ }} \\ & x=\angle BCD=\angle BGH={{120}^{\circ }} \\\end{align}$