

お菓子を三人でこうへいに分けよう。
先生は学生をこうへいに評価するべきです。
この会社は社員をこうへいに扱っていないと思います。
"こうへいに(公平に)" is in the lesson "Adverbs 2" (Level 31), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.