Descarta una carta, suma diez y resta dos.

They are affirmative informal commands for tú.

So the sentence is giving instructions to one person in an informal way:

• descarta = discard
• suma = add
• resta = subtract

For regular -ar verbs, the affirmative tú command is formed from the él/ella/usted present form:

• descartar → descarta
• sumar → suma
• restar → resta

Because Spanish often leaves out subject pronouns when they are understood from the verb form or the context.

So instead of saying:

• Tú descarta una carta, suma diez y resta dos.

Spanish normally just says:

• Descarta una carta, suma diez y resta dos.

This sounds more natural.

Because descarta is a command, while descartas is a statement.

Compare:

• Descarta una carta. = Discard a card.
• Descartas una carta. = You discard a card.

So the final -s matters a lot. Without -s, it is an instruction.

Because carta is a feminine singular noun, so it takes una.

• una carta = a card / a letter

In this sentence, carta most likely means card, especially in a game context.

So:

• un is for masculine singular nouns
• una is for feminine singular nouns

Since carta is feminine, un carta would be incorrect.

No. Carta can mean different things depending on context, especially:

• letter
• card
• sometimes even menu

In this sentence, descarta una carta strongly suggests card, because descartar is very common in card-game instructions.

So the context tells you which meaning fits.

Because carta is a noun that needs an article here, while diez and dos are being used as numbers by themselves.

• Descarta una carta = Discard a card
• Suma diez = Add ten
• Resta dos = Subtract two

In suma diez and resta dos, the object is just the number. Spanish does not need an article there.

If you wanted, you could make it more explicit with a noun:

• Suma diez puntos.
• Resta dos puntos.

But in many instructions, the noun is simply understood.

Because Spanish, like English, often uses commas to separate items in a series and y before the last one.

So this pattern is normal:

• Descarta una carta, suma diez y resta dos.

It works like:

• Do X, do Y, and do Z.

The y connects the final action to the rest of the list.

Yes, they are all regular -ar verbs.

Their infinitives are:

• descartar = to discard / to rule out
• sumar = to add
• restar = to subtract

Because they are regular, their affirmative tú commands are straightforward:

• descarta
• suma
• resta

This makes the sentence a nice example of standard command formation.

No. Descartar has a broader meaning.

It can mean:

• to discard something
• to rule out an option, idea, or possibility

Examples:

• Descarta una carta. = Discard a card.
• Podemos descartar esa opción. = We can rule out that option.

So in this sentence it has a game-related meaning, but the verb is useful in many situations.

The sentence as written is for one person, informal: tú.

Here are the other common versions:

Formal singular (usted)

• Descarte una carta, sume diez y reste dos.

Plural in Latin America (ustedes)

• Descarten una carta, sumen diez y resten dos.

So the original sentence is specifically the informal singular version.

Yes. It sounds natural, especially for:

• game rules
• classroom exercises
• step-by-step instructions
• math-style directions

Spanish often uses short command forms like this in instructions, without extra words. That is why the sentence feels direct and efficient.

A more expanded version is possible, but the original is perfectly natural.

The natural stress is:

• des-CAR-ta
• SU-ma
• RES-ta
• DIEZ
• DOS

None of descarta, suma, or resta needs a written accent mark because they already follow normal Spanish stress rules.

So the sentence is pronounced with clear stress on:

• -car- in descarta
• the first syllable in suma
• the first syllable in resta