Answer
\[d\ \vartriangle \ \left[ d\ \square \ \left( d\ \vartriangle \ d \right) \right]=b\].
Work Step by Step
Find\[d\ \vartriangle \ \left[ d\ \square \ \left( d\ \vartriangle \ d \right) \right]\]as,
\[\begin{align}
& d\ \vartriangle \ \left[ d\ \square \ \left( d\ \vartriangle \ d \right) \right]=d\ \vartriangle \ \left( d\ \square \ e \right) \\
& =d\ \vartriangle \ c \\
& =b
\end{align}\]
Hence, the value of \[d\ \vartriangle \ \left[ d\ \square \ \left( d\ \vartriangle \ d \right) \right]\]is \[b\].
