adverb
Adverb meaning something is done with little effort or trouble.
彼はその問題をわけなく解いた。
He solved the problem easily.
この仕事はわけなく終わるだろう。
This job will probably be finished without difficulty.
簡単に is more common and neutral; わけなく is slightly more emphatic about the lack of difficulty.
楽に emphasizes comfort or ease; わけなく emphasizes the absence of obstacles.
From 訳 (わけ, 'reason') + なく (adverbial form of ない, 'not'), literally 'without reason (for difficulty)'. The exact historical derivation is uncertain.