Brug Mix (reeks 1)

Reken uit

\(42 + 37 = \ldots\)

\(\begin{align} & 42 + 37\\= & \color{green}{40} + \color{red}{2} + \color{green}{30} + \color{red}{7} \\= & \color{green}{70} + \color{red}{9} \\= & \color{red}{79} \end{align}\)