Respuesta :

Perimeter (rectangle)=2(lenght)+2(width)
perimeter=24 cm
lenght =9 cm

Therefore:
24 cm=2(9 cm) + 2 width
24 cm=18 cm +2 width
2 width=24 cm -18 cm
2 width=6 cm
width=6 cm / 2=3 cm

Answer: width=3 cm.