Therefore, matrix $7 X$ is also of the same order.
Matrix $Z$ is of the order $2 \times p,$ i.e, $2 \times n \quad[\text { since } n=p]$
Therefore, matrix $5 Z$ is also of the same order.
Now, both the matrices $7 X$ and $5 Z$ are of the order $2 \times n$.
Thus, matrix $7 X-5 Z$ is well-defined and is of the order $2 \times n$.