Answer:
12cm
Step-by-step explanation:
1. Define the variable:
x = length of the rectangle
2x = width of the rectangle
2. Set the equation:
x + 2x is half of the rectangle
2(x + 2x) is the perimeter
So,
2(x + 2x) = 36
2x + 4x = 36
6x = 36
x = 6
Since x is the length, multiply it by 2 to find the width.
2x = 12