C is the brother or sister of J. That is represented as C - J or C * J.
I x C → I is the sister of C
I is the niece of J means - J's sibling ( brother or sister ) 's daughter is I.
Therefore, I is niece of J.
And this expressions above brings us to the conclusion that :
""I x C + N - J"" is the most appropriate and suitable answer. 
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