她答应下个月还清欠款。

She promised to ___pay back the debt next month.

他发誓要让那个背叛他的朋友付出代价。

He swore to ___pay back the friend who betrayed him.

我请他吃饭是为了报答他帮我修电脑。

I treated him to dinner to ___pay back his help with fixing my computer.