You change the topic from E to D, F to E, and find the corner bed: take point F in EC so that ∠CBF=20, then BF=BC, and ∠ BDC = ∠ BCD = 50, BC = BD = BF, and △ BFD is a regular triangle FB = Fe ∠ FBE =. . . (PS: It's a bit difficult. It's easy to remember. I wonder if the answer is right? ! The answer to your question should be 80. I wonder if the answer is right? ! )