我希望你能参加会议，但如果不，我会把笔记发给你。

I hope you can attend the meeting, but ___if ___not, I'll send you the notes.

画画时穿旧衣服。如果不，它们可能会被弄脏。

Wear old clothes when painting. ___If ___not, they might get stained.

经常保存你的工作。如果不，你可能会丢失进度。

Save your work frequently. ___If ___not, you might lose your progress.