Question: $(213 \times 657)^{-1}=213^{-1} \times$________.
Solution:
Let us assume the missing number be $x$ Then,
$=1 /(213 \times 657)=(1 / 213) \times(x)$
$X=213 /(213 / 657)$
$X=1 / 657$
$X=657^{-1}$
So, $(213 \times 657)^{-1}=213^{-1} \times \underline{657^{-1}}$
