Answer:
m∠BCD = 68.5°
Step-by-step explanation:
∠EDF corresponds to ∠DBC, so the two are congruent. The sum of that with ∠ABD is ∠ABC, which is supplementary to ∠BCD. That means the sum of the specified angles is 180°.
(3x +4) +(6x -8) +(7x -20) = 180
16x -24 = 180
16x = 204
x = 12.75
m∠BCD = 6x-8 = 6·12.75 -8
m∠BCD = 68.5°
