#1
Since the square has 4 equal sides
Since the perimeter of the square is the sum of the 4 sides, then
[tex]P=4s[/tex]P is the perimeter
s is the length of the side of the square
Since the side of the square is (3x - 7), then
Substitute s by (3x - 7) in the rule above
[tex]P=4(3x-7)[/tex]Multiply 4 by each term of the bracket
[tex]\begin{gathered} P=4(3x)-4(7) \\ P=12x-28 \end{gathered}[/tex]The expression of the perimeter is
[tex]12x-28[/tex]The answer is 12x - 28