This is the 9859th most frequent Japanese word.
解き
"解き" means "solution" or "unraveling" in English.
解く (toku) is used here to mean solving or figuring out a problem or question.
この問題を解くのは簡単です。
Solving this problem is easy.
解く (toku) here means to find the answer or resolve a mysterious issue.
彼はその謎を解いた。
He solved the mystery.
解く (toku) in this sentence refers to physically untying or loosening something.