坎儿井是新疆最古老的地下取水方式之一，其水源主要来自（　　）

解分式方程$\frac{2}{x-1}+\frac{x+2}{1-x}=3$时，去分母后变形为

Dear David,

    How are you? I'm fine. I'm in London, at the International School of English. I'm in Class 3 with eight other students.They're from different countries---Spain, America, and Thailand. Our teacher's name is Henry. He's very nice. He's a very good teacher.

    I'm living with an English family. Mr. and Mrs. Brown have three children. Tom is fourteen, Kate is twelve, and Andrew is seven. They are all very friendly, but it isn't easy to understand them.

    London is very big and interesting. The weather is good---cold but sunny---and the parks are beautiful! Hyde Park, and Green Park are all in the city center.

    English food is OK, but the coffee is very bad!

    Write to me soon.

Love

Paula