你通常花多长时间看电视？

How long does it take you to watch TV?
It take sb. 时间金钱 to do sth.花XXX时间金钱做XXX事

how long does it to watch

How long does it take you to watch TV

How long does it take you to watch TV ? 这个题主要考 it takes sb some time to do 这个句型

how long do you often watch TV?

How long does it take you to watch TV？