Element $u$ from some ring is an exceptional unit if both $u$ and $1-u$ are units, so if both $u$ and $1-u$ are invertible. In this work we first focus on the residue class rings modulo $n$, and then generalize it to all finite commutative rings with identity. In both cases, we first prove the formula for calculating the number of exceptional units, and then the formula for calculating the representations of any element in the ring as the sum of $k$ exceptional units.
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