Respuesta :
I'm assuming you're asking where the apostrophe should go. Apostrophes are for marking possession. In this sentence, the old MustangĀ belongs to Mr. Smith so it should go after his name:
Mr. Smith's old Mustang sounds like booming thunder when he starts it up.
Hope this helps!
Mr. Smith's old Mustang sounds like booming thunder when he starts it up.
Hope this helps!