For convenience, place the longer number on top
$7957\times 90$
Line up the numbers
$\begin{matrix}\:\:&7&9&5&7\\\times &\:\:&\:\:&9&0\end{matrix}$
Multiply the top number by the bolded digit of the bottom number
$\begin{matrix}\:\:&\bold{7}&\bold{9}&\bold{5}&\bold{7}\\\times &\:\:&\:\:&9&\bold{0}\end{matrix}$
Mutliply the bold numbers
$7\times 0=0$
$\frac{\begin{matrix}\:\:&7&9&5&\bold{7}\\\times &\:\:&\:\:&9&\bold{0}\end{matrix}}{\begin{matrix}\:\:&\:\:&\:\:&\:\:&0\end{matrix}}$
Mutliply the bold numbers
$5\times 0=0$
$\frac{\begin{matrix}\:\:&7&9&\bold{5}&7\\\times &\:\:&\:\:&9&\bold{0}\end{matrix}}{\begin{matrix}\:\:&\:\:&\:\:&0&0\end{matrix}}$
Mutliply the bold numbers
$9\times 0=0$
$\frac{\begin{matrix}\:\:&7&\bold{9}&5&7\\\times &\:\:&\:\:&9&\bold{0}\end{matrix}}{\begin{matrix}\:\:&\:\:&0&0&0\end{matrix}}$
Mutliply the bold numbers
$7\times 0=0$
$\frac{\begin{matrix}\:\:&\bold{7}&9&5&7\\\times &\:\:&\:\:&9&\bold{0}\end{matrix}}{\begin{matrix}\:\:&0&0&0&0\end{matrix}}$
Multiply the top number by the bolded digit of the bottom number
$\frac{\begin{matrix}\:\:&\bold{7}&\bold{9}&\bold{5}&\bold{7}\\\times &\:\:&\:\:&\bold{9}&0\end{matrix}}{\begin{matrix}\:\:&0&0&0&0\end{matrix}}$
Mutliply the bold numbers
$7\times 9=63$
$\frac{\begin{matrix}\:\:&\:\:&\:\:&\:\:&6&\:\:\\\:\:&\:\:&7&9&5&\bold{7}\\\:\:&\times &\:\:&\:\:&\bold{9}&0\end{matrix}}{\begin{matrix}\:\:&\:\:&0&0&0&0\\\:\:&\:\:&\:\:&\:\:&3&\:\:\end{matrix}}$
Add the carried number to the multiplication
$6+5\times 9=51$
$\frac{\begin{matrix}\:\:&\:\:&\:\:&5&\bold{6}&\:\:\\\:\:&\:\:&7&9&\bold{5}&7\\\:\:&\times &\:\:&\:\:&\bold{9}&0\end{matrix}}{\begin{matrix}\:\:&\:\:&0&0&0&0\\\:\:&\:\:&\:\:&1&3&\:\:\end{matrix}}$
Add the carried number to the multiplication
$5+9\times 9=86$
$\frac{\begin{matrix}\:\:&\:\:&8&\bold{5}&6&\:\:\\\:\:&\:\:&7&\bold{9}&5&7\\\:\:&\times &\:\:&\:\:&\bold{9}&0\end{matrix}}{\begin{matrix}\:\:&\:\:&0&0&0&0\\\:\:&\:\:&6&1&3&\:\:\end{matrix}}$
Add the carried number to the multiplication
$8+7\times 9=71$
$\frac{\begin{matrix}\:\:&7&\bold{8}&5&6&\:\:\\\:\:&\:\:&\bold{7}&9&5&7\\\times &\:\:&\:\:&\:\:&\bold{9}&0\end{matrix}}{\begin{matrix}\:\:&\:\:&0&0&0&0\\\:\:&1&6&1&3&\:\:\end{matrix}}$
Add the carried digit,
$7$, to the result
$\frac{\begin{matrix}\:\:&7&8&5&6&\:\:\\\:\:&\:\:&7&9&5&7\\\times &\:\:&\:\:&\:\:&9&0\end{matrix}}{\begin{matrix}\:\:&\:\:&0&0&0&0\\7&1&6&1&3&\:\:\end{matrix}}$
Add the rows to get the answer. For simplicity, fill in trailing zeros
$\frac{\begin{matrix}\:\:&\:\:&7&9&5&7\\\:\:&\times &\:\:&\:\:&9&0\end{matrix}}{\begin{matrix}0&0&0&0&0&0\\7&1&6&1&3&0\end{matrix}}$
Line up the numbers
$\begin{matrix}\:\:&\:\:&\:\:&9&0\\\times &7&9&5&7\end{matrix}$
$=716130$