=>
1. used to
2. used to
3. use to
4. use to
5. used to
6. to walk
7. use to
8. used to
9. be
10. use to
11. use to
12. used to travel
13. used to
14. use to like
15. use to
Used to V : đã từng
(+) S used to V
(-) S didn't use to V
(?) Did S use to V?

$\text{1.}$ used to 
$\text{2.}$ used to 

$\text{3.}$ use to  
$\text{4.}$ use to 

$\text{5.}$ used to 

$\text{6.}$ to walk 

$\text{7.}$ use to  
$\text{8.}$ used to 
$\text{9.}$ be 
$\text{10.}$  use to 
$\text{11.}$ use to 
$\text{12.}$ used to travel 

$\text{13.}$ used to 

$\text{14.}$ use to like 
$\text{15.}$ use to 

$\text{-> S + used to + V-inf+ O}$

$\text{-> S + didn't use to + V-inf + O}$
$\text{-> Did + S + use to + V-inf +O?}$

$#Ran$