## Intermediate Algebra (6th Edition)

$12x+4$
The perimeter of a square is equal to the sum of the length of each of its four sides. Also, we know that a square has four sides of equal length. Length of each side: 3x+1 $(3x+1)+(3x+1)+(3x+1)+(3x+1)=4\times(3x+1)=12x+4$