Question

Simplifique a expressão numérica 9 . 7 – 7 . 9 + 1 = ? ​

Answer 1

$\Large\boxed{\begin{array}{l}\sf9\cdot7-7\cdot9+1\\\sf\diagdown\!\!\!\!\!\!63-\diagdown\!\!\!\!\!\!63+1=1\end{array}}$