The area of a rectangle is equal to the length multiplied by the width, (l)(w).
What you want to do is make equations to solve this problem.
As the area of the rectangle is
, (l)(w) = 72, so l = (72/w).
You also know that l is 6cm longer than w, so l - 6 = w, or l = w + 6.
To solve for w, replace the l in the third equation to be the value of l from the first equation, so (72/w) = w + 6
Solve for w, and you get that w = 6, -12.
However, the width of a rectangle cannot be negative, so it must be 6 centimeters.
This way, if the length of the rectangle is 6cm longer than the width, it would be 12 cm. Then, the area of the rectangle would be (l)(w) = 12*6 = 72, which is the desired area.
The answer is 6 centimeters.
Hope this helped!