Er is gegeven dat $u_{1,1}=5$, $u_{1,2}=3$, $u_{1,1}=6$ en $u_{1,1}=8$.
Dan
$$\begin{align}
\sum_{k=1}^2 \sum_{j=1}^2 u_{k,j} & = \sum_{k=1}^2 (u_{k,1}+u_{k,2})\\
& = (u_{1,1}+u_{1,2})+(u_{2,1}+u_{2,2})\\
& = 5+3+6+8\\
& =22,
\end{align}$$
maar ook
$$\begin{align}
\sum_{j=1}^2 \sum_{k=1}^2 u_{k,j} & = \sum_{j=1}^2 (u_{1,j}+u_{2,j})\\
& = (u_{1,1}+u_{2,1})+(u_{1,2}+u_{2,2})\\
& = 5+6+3+8\\
& =22.
\end{align}$$