Zwei nette Personen haben dir (dative) eine Antwort (accusative) geschrieben. Beide haben dir gute Antworten geschrieben. Da kann ich nichts mehr sagen.

For a masculine substantive, its complementary object pronoun in accusative case is "ihn", whereas in dative case is "ihm". For a neutral substantive, its complementary object pronoun in accusative case is "es" (same as its nominative case), whereas in dative case is "ihm" (same as the dative case of a complementary object pronoun of a masculine substantive). So, if we have an example of, We give the ballpen (Kugelschreiber, m) to the teacher -- We give it to the teacher -- We give it to him (presuming in male gender) Then, in German, it becomes, Wir geben dem Lehrer den Kugelschreiber -- Wir geben ihn dem Lehrer -- Wir geben ihm ihn However, if we have an example of, We give the gift (Geschenk, nt) to the teacher -- We give it to the teacher -- We give it to him Then, in German, it becomes, Wir geben dem Lehrer ein Geschenk -- Wir geben es dem Lehrer -- Wir geben ihm es Take care and good day. / Mach's gut und schönen Tag.

There is more than dative in this sentence. The "teacher" is dative, while "it" is accusative. Dativ, the question is "Wem?" - Whom? The answer would be "Ihm." - (to) him Akkusativ, the question is "Wen/Was?" The Answer would be "ihn/sie/es". Wen/Was geben wir dem Lehrer? - Wir geben ihn(/sie/es) dem Lehrer.