Cada mes yo ahorro 15.000 pesos. This means: every month I save 15.000 pesos. “Ahorro” is the simple present conjugation of the verb “ahorrar” in the first person singular. “Ahorró” is wrong for two reasons: it’s in the preterite and it’s in the third person singular. If the sentence talks about “every month” it’s understood that the tense should be present because it’s referring to a habit or usual situation. “Ahorraron” is also in the preterite and is is in the third person of the plural. “Ahorra” is in the simple present but is conjugated in the third person of the singular.
