$\text{1.}$ Lan used to write to Mary twice a month . 

$\text{2.}$ Did they use to watch TV in the past ? 

$\text{3.}$ She used to be my idol when I was a child .

$\text{4.}$ There used to be a market here in 2005 . 

$\text{5.}$ She didn't use to know how to drive a car , but now she can drive well . 

→ used to + V-inf : đã từng làm j 

→ did not ( didn't)+ use to + V-inf

→ Did + S + use to + V-inf ? 

$#Lynkk$

$1. $ Lan used to write to Maryam twice a month

$2. $ Did they use to watch TV in the past ?

$3. $ She used to be my idol when I was a child

$4. $ There used to be a market here in 2005

$5. $ They didn't use to know how to drive a car, but now they can drive well

$→$ Used to được sử dụng để nói về một thói quen, hành động, sự kiện hoặc trạng thái đã từng xảy ra trong quá khứ và không còn xảy ra trong hiện tại nữa

$(+)$ S + Used to + V-bare

$(-)$ S + didn't + Use to + V-bare

$(?)$ Did + S + use to + V-bare ?

$→$ There used to be : Đã từng có

`@Chamian`