3 sentences

1. 我以为你算术不错呢。

   wǒ yǐ​wéi nǐ suàn​shù bù​cuò ne.

   I thought you were good at math.

   Source: OpenSubtitles

2. 这道算术题对他来说太简单了。

   zhèi dào suàn​shù tí duì tā lái shuì tài jiǎn​dān le.

   This arithmetic problem is too simple for him.

   Source: Dong Chinese Dictionary

3. 加法和减法是基本的算术运算。

   jiā​fǎ hé jiǎn​fǎ shì jī​běn de suàn​shù yùn​suàn.

   Addition and subtraction are basic arithmetic operations.

   Source: Dong Chinese Dictionary