It takes him half an hour to get to the airport.（对half an hour 提问）
问题描述：
It takes him half an hour to get to the airport.（对half an hour 提问）
答
How long does it take him to get to the airport?
答
How long takes his to get to the airport
答
画线提问：How long does it take him to get to the airport?
被画线处用How long替换,然后放到句子最前面.剩下的内容不变.因为是it,所以does.
这类句子均按这种方法做.