[Rusty]

Originally Posted by PieMage

2) Es absurdo: las entradas (tickets) / espectáculo / costar / tanto dinero
Es absurdo que las entradas para el espectáculo cuete tanto dinero. The highlighted verb contains a typo and doesn't agree in number with the subject in the subordinate clause. The use of 'que' and casting the verb in the subjunctive are correct.
3) Es increíble: (tú) no / conocer / novelas / Gabriel García Márquez
Es increíble que no conozca las novelas de Gabriel García Márquez. The verb doesn't agree in person with the subject of the subordinate clause. The sentence is fine, otherwise.
4) Sentimos: (nosotros) no / poder / ayudarlos a Uds.
Sentimos no poder ayduarlos a Uds. Typo. Everything else is correct, but some will argue in favor of using a subordinate clause. Try it that way if correcting the typo isn't the "problem."
5) Me molesta: haber / tanto / personas / que / hablar / durante / función
Me molesta que hay tantas personas que hable durante el función. Subjunctive must be used for the first verb. The second verb doesn't agree in number with the subject. The article doesn't agree with its object.

Hints given above.
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