If n= p, then the order of the matrix 7X$-$5Z is

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Option b is correct

$7X - 5Z = 7{X_{2 \times n}} - 5{Z_{2 \times p}}$

We can add two matrices if their order is same.
$n = p$

$\therefore$ Order of 7X$-$5Z is 2 × n.