Brug Mix (reeks 1)

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\(89 + 10 = \ldots\)

\(\begin{align} & 89 + 10\\= &10+89\\= &10 + \color{green}{80} + \color{red}{9} \\= & \color{green}{90} + \color{red}{9} \\= & \color{red}{99} \end{align}\)