2 sentences

1. 她每月给我们写三次信。

   tā měi​yuè gěi wǒ​men xiě sān​cì xìn.

   She writes to us three times a month.

   Source: AI Challenger 2017

2. 你应该每个月给自行车轮子加一次润滑油。

   nǐ yīng​gāi měi​gè yuè gěi zì​xíng​chē lún​zi jiā yī​cì rùn​huá​yóu.

   You should lubricate the wheels of your bicycle once a month.

   Source: UM-Corpus: Education