Basis Optellen

Reken uit

\(20 + 72 = \ldots\)

\(\begin{align} & 20 + 72 \\= & 20 + \color{green}{70} + \color{red}{2} \\ = & \color{green}{90} + \color{red}{2} \\ = & \color{red}{92} \end{align}\)