We know that the length of the rectangle is 9 cm, and it is equal in area to a square that has a perimeter of 24 cm. Since all sides of a square is equal, and a square has 4 sides, the area of the square would be 36. This is because 24/4 is 6, and 6*6 is 36. We now just need to find something multiplied by 9 that equals 36. In other words, 9x = 36. We can isolate 9 by dividing 9 from both sides. This gives us x = 4.
The width of the rectangle is 4 cm.