P2780
By direct computation
\begin{equation}
\begin{split}
X \times (Y \times Z)
& = \{ 0 \} \times (\{ 1 \} \times \{ 1 \}) \\
& = \{ 0 \} \times \{ (1, 1) \} \\
& = \{ (0, (1, 1)) \} \\
& \neq \{ ((0, 1), 1) \} \\
& = \{ (0, 1) \} \times \{ 1 \} \\
& = (\{ 0 \} \times \{ 1 \}) \times \{ 1 \} \\
& = (X \times Y) \times Z \\
\end{split}
\end{equation}
$\square$
