Thirty of them are Party members.(主语)
--- How many would you like?
--- Three ，please.(作宾语)
The nine boys are from Tianjing.(定语)
Six plus four is ten.(表语)
We four will go with you.(同位语)
(2) 暗示一个详细数字时，hundred, thousand, million一律不消复数;在暗示一个不确定命字时则用复数。譬喻：
Our country has a population of 1,300 million people.
There are three thousand students in our school.
After the war, thousands of people became homeless.
Maize is the most important food crop for millions of people in the world.
They arrived in twos and threes