El participante resuelve el rompecabezas.

In Spanish, it is very common to use an article like el, la, los, or las before a noun.

So el participante means the participant.
If you said only participante, it would usually sound incomplete in a normal sentence unless it appeared in a special context, like a label, heading, or after certain verbs.

In this sentence, el participante is the subject, so using el is the normal choice.

Yes, in this sentence el participante is masculine singular.

A useful thing to know is that participante is one of those nouns that can be masculine or feminine depending on the person:

• el participante = the male participant
• la participante = the female participant

The noun itself stays participante. Only the article changes.

Resuelve comes from the infinitive resolver, which means to solve or to resolve.

It looks different because Spanish verbs change form when they are conjugated.
Here, resuelve is the third-person singular present tense form:

• yo resuelvo = I solve
• tú resuelves = you solve
• él/ella/usted resuelve = he/she/you solve(s)

So resuelve matches el participante.

Because resolver is a stem-changing verb in the present tense.

The e in the stem changes to ue in many forms:

• yo resuelvo
• tú resuelves
• él/ella/usted resuelve
• ellos/ellas/ustedes resuelven

But not in nosotros or vosotros:

• nosotros resolvemos
• vosotros resolvéis (mostly Spain)

This kind of change is very common in Spanish.

Spanish often omits subject pronouns because the verb ending already tells you who the subject is.

So instead of saying:

• Él resuelve el rompecabezas

Spanish very often just says:

• Resuelve el rompecabezas

In your sentence, the subject is already clearly stated as el participante, so adding él would be unnecessary.

Yes, rompecabezas is masculine, so it takes el in the singular:

• el rompecabezas = the puzzle

Even though the word ends in -s, it is singular here. The article el tells you that.

Here it is singular: el rompecabezas.

This word is a compound noun, and its form is the same in singular and plural. The article tells you which one it is:

• el rompecabezas = the puzzle
• los rompecabezas = the puzzles

So yes, it may look plural to an English speaker, but in this sentence it is singular.

Because the personal a is normally used before direct objects that are specific people.

For example:

• Veo al participante. = I see the participant.

But el rompecabezas is a thing, not a person, so there is no personal a:

• Resuelve el rompecabezas.

That is completely normal.

Yes, resuelve is present tense.

In Spanish, the present tense can often translate into English in more than one way depending on context:

• he solves
• he is solving
• sometimes even he does solve

Without more context, resuelve simply tells you that the action is happening in the present.

The most neutral word order is:

• El participante resuelve el rompecabezas.

That is subject + verb + object, and it is the most natural basic order.

Spanish does allow some flexibility, but changing the order can change the emphasis:

• El rompecabezas lo resuelve el participante.
  = It’s the participant who solves the puzzle.

So yes, word order can change, but the original sentence is the most straightforward version.

In most of Latin America, resuelve is pronounced approximately like:

• reh-SWEL-beh

A few details:

• r in resolver/resuelve is a light tapped r
• ue sounds like we
• v in Spanish often sounds more like a soft b
• the final e is pronounced, unlike in English

So it is not like English resolve. The Spanish pronunciation is clearly syllabic: re-suel-ve.

In most of Latin America, z is pronounced like s.

So rompecabezas sounds approximately like:

• rom-pe-ca-BE-sas

In most of Spain, the z would sound more like the th in thin, but in Latin American Spanish it is generally an s sound.

Yes. If the context is already clear, you could use a subject pronoun:

• Él resuelve el rompecabezas. = He solves the puzzle.

But Spanish often prefers to omit the subject pronoun entirely:

• Resuelve el rompecabezas.

That sounds very natural if everyone already knows who is being talked about.

El rompecabezas is the direct object.

It is the thing receiving the action of the verb:

• el participante = the subject, the person doing the action
• resuelve = the verb
• el rompecabezas = the direct object, the thing being solved

So the structure is:

subject + verb + direct object

It most commonly means puzzle, especially something like a puzzle or brainteaser.

Depending on context, it can also be used more figuratively for something puzzling or difficult to figure out. But in a basic sentence like this, a learner should usually understand it as puzzle.

If you want to know exactly which kind, context would tell you more.