Difficult to solve; not easily resolved—used for problems, puzzles, or issues that are hard to untangle.
この数学の問題は構造が複雑で、とても解き難い。
This math problem has a complex structure and is very difficult to solve.
彼女の心の傷は深く、簡単には解き難いものがある。
Her emotional wounds are deep and not easily resolved.
古い暗号は解き難く、専門家でも時間がかかることがある。
Old ciphers are hard to crack and can take experts a long time.
文法的に正しいが意味が取りにくく、解き難い文だ。
It's grammatically correct but hard to interpret—a sentence that's difficult to unravel.