Basis Optellen

Reken uit

\(40 + 37 = \ldots\)

\(\begin{align} & 40 + 37 \\= & 40 + \color{green}{30} + \color{red}{7} \\ = & \color{green}{70} + \color{red}{7} \\ = & \color{red}{77} \end{align}\)