• 答こたえる — to answer
• 回答かいとう — reply / response
• 解答かいとう — solution (to a question)
• 応答おうとう — reply / response
• 答案とうあん — answer / examination paper
• 返答へんとう — reply / answer
• 即答そくとう — immediate reply
• 贈答品ぞうとうひん — gift item

The top radical ⺮ represents bamboo — once used to make writing materials. The lower part 合 implies a coming together. The character originally referred to a formal reply or response, especially one written on bamboo slips.

先生せんせいの質問しつもんに答こたえました。
I answered the teacher’s question.

その問題もんだいの答こたえが分わかりません。
I don’t know the answer to that question.