亚历克斯当时十二岁。

Alex was twelve years old.

在纽约，现在是十二点。

In New York, it's twelve o'clock.

自行车上有十二个男孩。

There are twelve boys on the bike.

我们在十二点半吃午饭。

We have lunch at half past twelve.

他打算做十二个这样的。

He was going to do twelve of these.