Rules of replacement are slightly different from the previous rules.
Instead of being mini proofs that let you derive something new, they only assert that if you have one of the statements listed, you can substitute the other, because they are logically equivalent. Because of this, you only need one line for justification. Note that they work in both directions. You can start with the statement on either side and substitute the other. Since you don't derive anything new with these rules, you couldn't work a whole proof using just these rules.