Bonjour,
Réponse :
a. He/not/left/ Mexico / have / should.
He should not have left Mexico.
b. could/kept / situation / their / Larissa andMayte/have/secret.
Larissa and Mayte could have kept their situation secret.
c. If / had/known /they/they/ not / wanted /live/to/American / would / have / the /Dream.
If they had known, they would not have wanted to live the American Dream.
( S'ils avaient su, ils n'auraient pas voulu vivre le rêve américain. )
;)