The Total solution for NCERT class 6-12
In figure, if AB ||CD and CD || EF, find ∠ACE.
Given: CD || EF
∠ FEC + ∠ECD = 180°
[Sum of co-interior anglesis supplementary to each other]
=> ∠ECD =180° – 130° = 50°
Also, BA || CD
=> ∠BAC = ∠ACD = 70°
[Alternative angles ofparallel lines are equal]
But, ∠ACE + ∠ECD =70°
=> ∠ACE =70° — 50° = 20°