hi !
1) oui, je leur dis la vérité
je dis la vérité à qui = à mes parents = 3éme p. plural = leur = them
I told them the truth
2) oui, nous lui parlons
nous parlons à qui ? à notre employeur = lui
3ére p. sing = lui
vous parlez à votre employeur = votre = your
are you talking to your employer ? Yes, we're talking to him
3) oui elle vous écrit une lettre.(nous = 2ère p. pluriel)
is she writing us a letter ? Yes, she is is writing you a letter
you = vous (2eme p. sing masc.
lui would have been him = you're writinfng him a letter
me would have been : vous m'écrivez une lettre = you're writing me a letter
hope I helped !!