Answer
If $\left[ \begin{matrix}
3 & x \\
y & -7 \\
\end{matrix} \right]=\left[ \begin{matrix}
3 & -10 \\
6 & -7 \\
\end{matrix} \right]$, then $x=-10$ and, $y=6$
Work Step by Step
It is given that,
$\left[ \begin{matrix}
3 & x \\
y & -7 \\
\end{matrix} \right]=\left[ \begin{matrix}
3 & -10 \\
6 & -7 \\
\end{matrix} \right]$
The two matrices are equal only when the corresponding elements of both the matrices are equal.
That is,
$\begin{align}
& 3=3 \\
& x=-10 \\
& y=6 \\
\end{align}$
And,
$-7=-7$
Hence, $x=-10\text{ and }y=6$
