SOLUTION: If m∠A=60° and m∠B=80° then m∠BCD=

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Question 1038355: If m∠A=60° and m∠B=80° then m∠BCD=
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!

The measure of an exterior angle of a triangle is equal to 
the sum of the measures of the two remote interior angles.
∠A and ∠B are interior angles of ∆ABC and ∠BCD is an
exterior angle of ∆ABC.   

Therefore:  m∠BCD = m∠A + m∠B = 60° + 80° = 140° 

Edwin