Perimeter of a rectangle= 2(length)+2(width)
Data:
Perimeter=108 cm
length=18 cm
therefore:
108 cm=2(18 cm)+2(width)
108 cm=36 cm+2 (width)
2 width=108 cm -36 cm=
2 width=72 cm
width=72cm/2
width=36 cm
Answer: the width of the picture frame would be 36 cm.