1. It takes maria eleven hours to fly from Canada to China today.
. =Maria spends eleven hours flying form Canada to China today
解析：
It takes sb some time to do sth 做某事花費(fèi)某人多長時間
sb spend some time doing sth某人做某事花費(fèi)多長時間
2.i don't know how i can swim in the river
=I don't know how to swim in the river. 我不知道怎么樣在河里游泳.
how有一個用法是how + to do(即：how + 動詞不定式)
Eg：
Can you tell me how to learn English well?
這句話相當(dāng)于：Can you tell me how I can learn English well?
當(dāng)省略主語、謂語不至于引起含義不明時,可以直接用how to do來表達(dá).