The first thing we must do for this case is to define variables.
We have then:
x: sides of the triangle
y: sides of the square
The perimeter of the triangle is:
[tex]p1 = 3x
[/tex]
The perimeter of the square is:
[tex]p2 = 4y
[/tex]
We now write the system of equations that models the problem.
The side of a triangle with 3 equal sides is 7 inches shorter than the side of a square:
[tex]x = y - 7
[/tex]
The perimeter of the square is 39 inches more than the perimeter of the triangle:
[tex]4y = 3x + 39
[/tex]
Resolving the system graphically we have that the solution is the ordered pair:
[tex](x, y) = (11, 18)[/tex]
Note: See attached image for graphic solution.
Answer:
The length of a side of the square is:
[tex]y = 18 inches[/tex]
