1. 字母x代表未知数。

[ zì mǔ x dài biǎo wèi zhī shǔ 。 ]

The letter "x" stands for an unknown number.

2. 甲壳虫乐队代表了他们时代的部分精神。

[ jiǎ qiào chóng yuè duì dài biǎo le tā mén shí dài de bù fēn jīng shén 。 ]

The Beatles represented part of the spirit of their age.

3. 我代表我们公司欢迎你来这里。

[ wǒ dài biǎo wǒ mén gōng sī huān yíng nǐ lái zhè lǐ 。 ]

On behalf of my company, I would like to welcome you here.