If w is the width of the rectangle, then, you have for the length l of the rectangle:
l = 3w + 2
take into account that the perimeter of the rectangle is 46, and the expresionf for the perimeter P is:
P = 2l + 2w
in order to determine the value of the length l, replace the expression
l = 3w + 2 into the expression for the perimeter P, then, solve for w:
P = 2(3w + 2) + 2w
P = 6w + 4 + 2w
P = 8w + 4
replace P = 46:
46 = 8w + 4
46 - 4 = 8w
42 = 8w
42/8 = w
21/4 = w
5.25 = w
replace the previous value of w into the expression l = 3w + 2
l = 3(5.25) + 2
l = 17.75
Hence, the length of the rectangle is 17.75