DBE forms a straight line measuring 180°

∠CBE is 50° {angles of a triangle add up to 180°.....90° and 40° are given in that triangle}

∠ABD is 60° {angles of a triangle add up to 180°.....90° and 30° are given in that triangle}

∠ABC = 180° - 50° - 60° {all angles making up ∠DBE add up to 180°}

∠ABC = 70°

**K.) 70°**

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