Respuesta :

Exvited
[tex]12r+5s-7t+11r+9s-4r \\ \\ (12r + 11r - 4r) + (5s + 9s) - 7t \ / \ gather \ the \ like \ terms \\ \\ 19r + 14s - 7t \ / \ simplify \\ \\ [/tex]

So, your answer to this problem is 19r + 14s - 7t.