Answer:
x = 3/16
Explanation:
Square's perimeter must equal triangle's perimeter. Using the given formulas for the two different perimeters, we obtain the equation
5x + 6 = 3(7x + 1), where 5x + 7 includes all four sides of the square and
7x + 1 includes all three sides of the triangle.
Performing the indicated multiplication, we get 5x + 6 = 21x + 3.
Combining like terms results in 3 = 16x.
Solving this last equation for x, we get x = 3/16.