The word 'they' is a pronoun, a personal pronoun, a word that takes the place of a plural noun (or two or more nouns) as the subject of a sentence or a clause.
The word 'problem' is a noun as a word for something that causes trouble or difficulty; a word for a question proposed for solution or discussion; a word for a thing.
The word 'problem' is an adjective used to describe a noun as difficult to deal with.
"They must settles this problem themselves."The pronouns in the sentence are:they (personal pronoun)themselves (reflexive pronoun)The word 'this' can be a demonstrative pronoun when it takes the place of a noun in a sentence but in this sentence it is an adjective used to describe the noun 'problem'.
The subject pronouns are I, you, we, he, she, it, and they. Example sentences:I saw that movie.You have a phone call.They loved the cake that we brought.He said that it was delicious.She could not complete the math problem.
To be honest, making an error with pronouns once in a while doesn't affect writing too much. But when pronouns or anything else is consistently incorrect, it makes the writing difficult to understand and tends to give the reader the impression that you may not know what you're talking about, since you don't know the basic grammar. If using pronouns correctly is a problem for you (we all have our own difficulties with English grammar) and you are required to write an essay, thesis, or business report then the best course of action is to be aware of your problem and keep a simple guide to pronouns available when you write. See the link below for an easy to understand guide.
The most commonly used pronouns are:personal pronouns: I, you, we, he, she, it, me, us, him, her, they, them.adjective pronouns: my, your, his, her, their, its.interrogative pronouns: who, whom, what, which, whose.
The singular objective pronouns are me, you, him, her, and it. The plural objective pronouns are us, you, and them.
The object pronouns are: me, us, him, her, and them.The pronouns you and it are both subject and object pronouns.
Pronouns that refer mostly to people are called personal pronouns. Some personal pronouns include I, me, you, him, her, she, them, he, and they.
Object pronouns are the pronouns that can only be used as the direct object or an indirect object of a sentence or phrase. The direct object pronouns are pronouns that are being used as the direct object of a sentence.The object pronouns are me, him, her, us, them, whom, whomever.There are some pronouns that can be subject or object pronouns; they are you, it, which, that, what, everybody.
Object pronouns or objective pronouns are pronouns that are used only for the object of a sentence or phrase.The objective pronouns are me, us, him, her, them, that, and those.Some pronouns can be used as the subject or the object of a sentence or phrase, they are you and it.
Subject pronouns: I, you, he, she, etc. Object pronouns: me, you, him, her, etc. Possessive pronouns: mine, yours, his, hers, etc. Possessive determiners: my, your, his, her, etc. Reflexive pronouns: myself, yourself, himself, herself, etc.
Object pronouns take the place of a noun as the object of a sentence or phrase. Some objective pronouns are me, us, him, her, and them. Some objective pronouns are used for both subject and object, they are youand it.
Pronouns that can be objective or subjective are you, it, here, and where.