Simply
Merely, Only
adverb
If you're moving towards (に) simple, you're saying simply, merely, or only.
If you know the readings of your kanji you'll know how to read this as well.
単に安い
simply inexpensive
単に見る
to simply look at
単にある
to simply be, to simply exist
単にラッキーだっただけですよ。
It was just pure luck, that's all.
単にフラれただけですよ。
I just got dumped, plain and simple.
彼は単に勉強ができるだけでなく、スポーツや音楽にも才能があります。
He not only excels in academics but he also has talent in sports and music.