In the following sentence, should "Who", "Whom", "Whoever," or "Whomever" be used in the blank space?: ____ tried to fix the computer also fixed the printer.
Who is used with a subject: "Who fixed that computer?"
Whom is used with a direct object or an indirect object.
"whom is that woman chasing?"- direct
"to whom is that boy running?"-indirect object
Whomever is not used any more, it may be archaic I'm not sure. Instead use whomsoever which is the object form of whoever.