Answer:
Length --> x
Width --> y
Perimeter of a rectangle --> 2x + 2y
The length is always 4 cm more than double the width
x - 4 = 2y
y = (x-4)/2
x = 2y + 4
a. The polynomial equation to give the perimeter --> 2(2y+4) + 2((x-4)/2)
b. x - 4 = 2·6 --> x - 4 = 12 --> x = 16
Perimeter --> 2·16 + 2·6 = 44 cm