$$\begin{array}{rrr}
\mathbf{9} & \mathbf{4} & \mathbf{20} \\
\mathbf{8} & \mathbf{5} & \mathbf{12} \\
\mathbf{7} & \mathbf{6} & \mathbf{\textcolor[rgb]{150,0,0}{?}} \\
\end{array}$$
? = Was ist die Antwort!
$$\begin{array}{rrrrlr}
\mathbf{9} & & \qquad \mathbf{4} & & \qquad \mathbf{20} & \\
& -1 & & +1 & & -8 \\
\mathbf{8} & & \qquad \mathbf{5} & & \qquad \mathbf{12} \\
& -1 & & +1 & & -8 \\
\mathbf{7} & & \qquad \mathbf{6} & & \qquad \mathbf{\textcolor[rgb]{150,0,0}{12-8=4}} \\
\end{array}$$
.
$$\begin{array}{rrr}
\mathbf{9} & \mathbf{4} & \mathbf{20} \\
\mathbf{8} & \mathbf{5} & \mathbf{12} \\
\mathbf{7} & \mathbf{6} & \mathbf{\textcolor[rgb]{150,0,0}{?}} \\
\end{array}$$
? = Was ist die Antwort!
$$\begin{array}{rrrrlr}
\mathbf{9} & & \qquad \mathbf{4} & & \qquad \mathbf{20} & \\
& -1 & & +1 & & -8 \\
\mathbf{8} & & \qquad \mathbf{5} & & \qquad \mathbf{12} \\
& -1 & & +1 & & -8 \\
\mathbf{7} & & \qquad \mathbf{6} & & \qquad \mathbf{\textcolor[rgb]{150,0,0}{12-8=4}} \\
\end{array}$$