The relation between the width and the length is : l = 3w +4 -- eqn (1) Perimeter = 56 » 2w + 2l = 56 Dividing through by 2 gives; w + l = 28 w = 28 - l -- eqn(2) Substitute eqn (2) in eqn (1) » l = 3(28-l) +4 Expanding bracket gives; l = 84 - 3l +4 Grouping like terms , we have; l + 3l = 84+4 4l = 88 l = 88/4 l = 22 The length of the rectangle is 22 units.