$\text{9.I/like/read/books/my free time}$

$\text{→ I like reading books in my free time}$

$\text{10.Tet/be/most/important celebration/Vietnamese people}$

$\text{→ Tet is the most important celebration for Vietnamese people}$

$\text{11.Hung/take part in/different activities/town/recently}$

$\text{→ Hung has taken part in different activities in the town recently }$

$\text{12.Mount Pinatubo/the Philippines/erupt/1991}$

$\text{→ Mount Pinatubo in the Philippines erupted in 1991.}$

9. I like reading books in my free time

10. Tet is the most important celebration for Vietnamese people

11. Hung has taken part in different activities in the town recently 

12. Mount Pinatubo in the Philippines erupted in 1991.