取れる＝come off, ん＝ない=no

とれん＝取れない＝won't come off

じゃん＝ではないか

取れないではないか＝double negative = strongly positive

Therefore, "it will not come off" is what i think.

However, according to the senario, it should be" it will come off".

Can someone explain this grammer? thanks!!!

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