Since, BD||AE and CG is transversal.
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Therefore,∠BCH=∠EHC⇒∠BCH=120∘
Again CG ||DF and BD is transversal.
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Therefore,∠BCH=∠CDE⇒∠CDE=120∘
Also, AB||CG and BC is transversal.
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Therefore∠ABC+∠BCH=180∘⇒∠ABC=180∘−120∘⇒∠ABC=60∘
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