Faltar con dativo: carencia y cantidad restante

In Spanish, faltar works like gustar: the indirect object pronoun (me/te/le…) shows who is missing something, and the verb agrees with what is missing. "Dos páginas" is plural, so we use "faltan". You can review this pattern in the “gustar y similares” section of the grammar.

"Nos faltan 30 minutos" = "we are 30 minutes short / we’re missing 30 minutes (to reach the needed amount)". In everyday speech, people often say things like "me faltan horas al día" (literally, "I’m missing hours in the day").

We describe the situation without saying "to whom" something is missing: three invoices are missing. The subject is "tres facturas" (plural), so we say "Faltan".

A very typical question is "¿Qué te falta…?". The interrogative "qué" is usually treated as singular, so we use "te falta".

The indirect object pronoun goes before the verb: "me falta". "Nada" is singular, so we use "falta". The other options are either grammatically incorrect or change the person/meaning.

The subject is "dos personas" (plural), so we use "faltan".

"Nos faltan 5 minutos" = "we’re missing 5 minutes / we are 5 minutes short". This is a natural way to express how much time is missing to reach a goal.

The pattern is the same as with "gustar": indirect object pronoun "le" (for whom) + verb agreeing with what is missing. "Un documento" is singular, so we say "le falta". You can read more about this pattern in the "gustar y similares" section.