xiān / zhǎo / chū / shí / èr / hé / shí / bā / de / gōng / yuē / shù / zài / jì / suàn / tā / men / de / zuì / dà / gōng / yuē / shù

先找出十二和十八的公约数，再计算它们的最大公约数。

First find the common factors of twelve and eighteen, then calculate their greatest common divisor.