9- The students talked to ... teacher.
The students talked to his their teacher.

-Students=Plural

10- Mrs.Johnson walked to .... car.
Mrs. Johnson walked to his her car.

-Mrs. = Female

Unit 8 - Exercise 1

1- Sally is carrying.....purse.
Sally is carrying her purse.

2- Tom and Carol are walking to .... house.
Tom and Carol are walking to their house.

3- The boys are writing in ... notebooks.
The boys are writing in their notebooks.

4- The girls are reading ... books.
The girls are reading their books.

5- Mary is wearing ... hat.
Mary is wearing her hat.

6- Tom is wearing ... gloves.
Tom is wearing his gloves.

7- Dick and Ann are wearing ... coats.
Dick and Ann are wearing their coats.

8- Mr. Tompkins carried ... briefcase.
Mr. Tompkins carried his briefcase.

9- The students talked to ... teacher.
The students talked to their teacher.

10- Mrs. Johnson walked to .... car.
Mrs. Johnson walked to her car.

Other than quesitons 9 and 10, your answers are perfect :)

for 9, since "students" is plural, you would use "their" instead of "his"

for 10, since MRS is used for women, you would use "her" instead of "his"

Keep challenging yourself and studying and you'll have English in no time.

Hope this helped :)