In the sentence, "When Sarah and her mom went to the store, she bought a new jacket," this is the reason the sentence is confusing.
What is because "she" could refer to either Sarah or her mom (ambiguous antecedent)?
Grammatically speaking, words like everyone, anybody, and nobody are always considered this number (singular or plural).
What is Singular?
This is the specific mistake made when a sentence starts in the third person (he, she, a person) but randomly switches to you.
What is a point-of-view shift (or shift in person)?
In the sentence, "Before the students took the test, they reviewed their notes," this specific noun is the antecedent for "they."
What is Students?
This is the formal correction for the exit ticket sentence: "Each of the girls gave their opinion."
What is "her opinion" (or rewriting to "All of the girls gave their opinions")?
This is the corrected version of this sentence: "When a person walks into the classroom, you can feel the tension."
What is "When a person walks into the classroom, he or she can feel the tension" (or "When you walk... you can feel...")?
In the sentence, "Neither the coach nor the players brought their jerseys," this specific noun is the antecedent that forces the pronoun to be plural.
What is players (the noun closer to the pronoun)?
To fix the sentence, "Everyone needs their notebook," for formal writing without using "his or her," you should change the subject ("Everyone") to this plural alternative.
What is "All students" (or "All people")?
In formal writing, pronouns like I, me, and we belong to the first person, you belongs to the second person, and he, she, they, and it belong to this person.
What is third person?