Ambuguity of CFG

Hello,

I know that all simple grammars have the special property that they're
unambigous grammars. I was trying to prove by using the fact that all
DFA/NFA and R.E.s are equiv. to CFG and that they hold a single
solution and therefore create an unambigous grammar. The problem with
this statement is that not all CFG are regular, so I was wondering if
anyone had another insight on how to prove this statement so that I can
say it holds. Thank you in advance.

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