the correct question is
Isaac made all these rectangles with 24cm lengths of string. This implies that the perimeter of all these rectangles are equal. What do we observe about the sum of the length and the width?
Let
x-----------> the length of rectangle
y-----------> the width of rectangle
we know that
[perimeter of rectangle]=2x+2y
24=2x+2y------------> 12=x+y
the answer is
it is observed that in all the rectangles the sum of its length and its width will be equal to 12