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Reken uit

\(9 + 42 = \ldots\)

\(\begin{align} & 9 + 42 \\= & 42 + 9 \\= & 42 + \color{green}{8} + \color{red}{1} \\= & \color{green}{50} + \color{red}{1} \\= & \color{red}{51} \end{align}\)