Can you clarify the ambiguity of someone's quote by using square brackets within their quote?

if the person who you are quoting has left out a Word. "He went to the shop where got some coke"... "he went to the shop where [he] got some coke"

or

you are only using half the quote and so it appears to not make sense, George Bush said "Osama is a terrorist and i will go find him and fight him myself". Press might say George Bush said today that he is planning to "go find him [Osama] and fight him".

or

the quote they said may have made sense but you need to add in a Word because you are changing the context.

ie. In the story Tomorrow, When the War Began, Ellie is clearly a very strong girl, as indicated when she "ran accross the crowded bridge and finally got what I [she] was looking for... My [her] mother." - original quote would have been "I ran accross the crowded bridge and finally got what I was looking for... My mother."