A renda paga a despesa fixa.

They are doing two different jobs:

• The first A is the definite article the and goes with renda: A renda = the income.
• The second a is also the definite article the, but it goes with despesa fixa: a despesa fixa = the fixed expense.

So even though both words are spelled a, they belong to different noun phrases.

Paga is the 3rd person singular form of the verb pagar in the present tense.

• pagar = to pay
• ele/ela/você paga = he/she/you pay(s)

The subject here is a renda, which is singular, so the verb must also be singular:

• A renda paga = The income pays / covers

If the subject were plural, the verb would change:

• As rendas pagam... = The incomes pay...

Here it is a verb.

You can tell because it comes right after the subject a renda and introduces what is being paid: a despesa fixa.

So the structure is:

• A renda = subject
• paga = verb
• a despesa fixa = direct object

It is true that pago/paga can also be an adjective or past participle in other contexts, but not in this sentence.

Portuguese often uses the definite article where English would not.

In English, we often say:

• Income covers the fixed expense

In Portuguese, it is very common and natural to say:

• A renda paga a despesa fixa

Leaving out the article can sound unnatural in a normal sentence, unless you are writing something very telegraphic, like a title, label, or note.

In Portuguese, adjectives usually come after the noun.

So:

• despesa fixa = fixed expense
• noun: despesa
• adjective: fixa

That is the normal word order. Putting fixa before the noun would sound unusual here and could change the tone or emphasis.

Because adjectives in Portuguese usually agree with the noun in gender and number.

• despesa is a feminine singular noun
• so the adjective must also be feminine singular
• fixo becomes fixa

Compare:

• o custo fixo = the fixed cost
• a despesa fixa = the fixed expense
• as despesas fixas = the fixed expenses

No. Pagar normally takes a direct object when you say what is being paid.

So:

• pagar a despesa = to pay the expense
• pagar a conta = to pay the bill

That is why there is no preposition between paga and a despesa fixa.

However, with a person, Portuguese may use a different structure depending on what exactly is meant. But in this sentence, a despesa fixa is simply the direct object.

Yes. For example:

• As rendas pagam as despesas fixas.

Everything changes to match the plural:

• A → As
• renda → rendas
• paga → pagam
• a despesa fixa → as despesas fixas

This is a good example of agreement working across the sentence.

It follows the very common Portuguese pattern:

subject + verb + object

So:

• A renda = subject
• paga = verb
• a despesa fixa = object

This is the same basic order English usually uses, which makes the sentence straightforward for an English speaker.

Not exactly.

• despesa = expense
• conta = bill/account
• gasto = spending/expense/cost in many contexts

Despesa fixa is a broader financial term, often used for a regular fixed expense in a budget, such as rent, insurance, or a subscription.

A conta is more specifically a bill or account, such as:

• conta de luz = electricity bill
• conta de água = water bill

So despesa fixa is the more natural term in budgeting language.

Approximately:

a HEN-da PA-ga a des-PE-sa FIK-sa

A few notes:

• renda: the r at the beginning is usually pronounced like an English h in Brazilian Portuguese.
• despesa: stress on pe
• fixa: the x here sounds like sh in many Brazilian pronunciations, so it sounds like FIK-sha

Pronunciation varies somewhat by region, but that is a good general Brazilian pronunciation guide.