\begin{frame}[t]
  \begin{block}{}
  \begin{center}
  $\begin{array}{llcl}
  (1)&e\cdot x&\to&x\\
  (2)&I(x)\cdot x&\to&e\\
  (3)&(x\cdot y)\cdot z &\to& x\cdot (y\cdot z)\\
  (4)&I(x)\cdot (x\cdot z)&\to& z\\
  (8)&y\cdot e&\to& y\\
  (9)& I(I(y)) &\to& y\\
  (10)&I(e)&\to& e\\
  (11)&y\cdot I(y)&\to& e\\
  (12)&y\cdot (I(y) \cdot x) &\to& x\\
  (13)&x\cdot (y\cdot I(x\cdot y)) &\to& e\\
  (14)&y\cdot I(x\cdot y)&\to& I(x)
  \end{array}$
  \end{center}
  \end{block}
    
  \bigskip
  \bigskip

  Removing the redundant reduction rule (13):\pause
  $$x\cdot (y\cdot I(x\cdot y))\;\to_{14}\;  x \cdot I(x) \;\to_{11}\; e$$
\end{frame}