The length of the rectangle is 3 times its width. Find the area of this rectangle if its perimeter is 96 cm.

Let X be the width of the rectangle, then the length will be 3X. The perimeter of the rectangle is twice the sum of the length and width 2 * (X + 3X). If the perimeter of the rectangle is 96, then make up the equation.
2 * (X + 3X) = 96
2X + 6X = 96
8X = 96
X = 96: 8
X = 12
Since X = 12 is the width of the rectangle, then the length is 3 * 12 = 36.
Verification:
2 * (12 + 36) = 96
2 * 48 = 96
96 = 96
Answer: 12; 36.