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In the diagram below, AB and EF are parallel. If angle ABC = 120 degrees, angle BCD = 180 degrees, and angle ECD = 55 degrees, then what is angle CEF, in degrees?

 

 

 Apr 17, 2020
 #1
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Continue line EF to the left so that it intersects line BCD at point X

 

Since FEX is parallel to AB, angle(CXE)  =  180o - angle(ABC)  =  180o - 120o  =  60o.

 

In triangle(CXE), angle(CXE) = 60o and angle(ECD) = 55o, so angle(XEC) = 65o.

 

This means that angle(CEF) = 115o.

 Apr 17, 2020

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