By adding a third parallel line to the diagram, find ABC?

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1 Answer
CW
Aug 1, 2017

#angleABC=75^@#

Explanation:

enter image source here

Add the third line, parallel to lines #M and N#, through the vertex B, as shown in the figure. This splits #angleABC# into two smaller angles, #x and y#.

#z=180-150=30^@#

By the parallel lines properties, #x=45^@ and y=z=30^@#.

So #angleABC=x+y=45+30=75^@#

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