My grandfather passed away when I was fifteen.我爷爷去世的时候我十五岁

pass away:逝世

His mother passed away last year.

他母亲去年去世了。

That famous mathematician passed away yesterday.

昨天，那位著名的数学家去世了。

And then he just burst out laughing.后来他也大笑了出来

burst out:突然 ... 起来； 大声叫喊

He burst out crying like a child.

他像孩子一样忽然哭起来。

She burst out laughing and then checked herself.

她突然爆笑起来，然後又突然止住。

I just found out about the website,我只是刚刚才发现那个网站

find out:发现；找出来

We shall find out the truth early or late.

我们迟早会查明事实真相。