Denshi Jisho — Online Japanese dictionary

解く とく 1: to solve; to answer;
2: to untie;
3: to comb; to untangle (hair)
Common word, Godan verb with ku ending, Transitive verb 
解く ほどく to unfasten; to untie; to unwrap (e.g. parcel)
Common word, Godan verb with ku ending, Transitive verb, Usually written using kana alone 

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