1. Fill in the same digit in the $\square$ below to make the equation true.
$$
97+\square \times(19+91 \div \square)=321, \quad \square=
$$
$\qquad$
【Analysis】 7
$$
\begin{aligned}
97+\square \times(19+91 \div \square) & =321 \\
97+\square \times 19+\square \times 91 \div \square & =321 \\
97+\square \times 19+91 & =321 \\
\square \times 19 & =133 \\
\square & =7
\end{aligned}
$$