Used to is used for a habit in the past.

               

I used to play football a lot.

They used to go on holiday abroad. 

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question/negative:

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Did you use to play football a lot?

They didn't use to go on holiday abroad.

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Be used to is used for when you are accustomed to something..

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I am used to going to school by bike.

They are used to living in the middle of nowhere.

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question/negative:

Are you used to going to school by bike?

They aren't used to living in the middle of nowhere.

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Get used to means get accustomed to. 

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You to get accustomed to travelling if you often go abroad.

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question/negative:

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Do you  get accustomed to ....?

You don't get accustomed to ......