Respuesta :
The figure is not given for this question. It would be more helpful if you understand what is a perimeter. The sum of the side lengths of a shape is called the perimeter. A quadrilateral is a polygon with four edges which means four side. Side KL should be one of them. The length of this side should be 90 minus the 3 side lengths. Hope this could help.
Answer;
-13 cm
Explanation;
The perimeter of quadrilateral JKLM is 90 centimeters.
JK = n + 7
KL = n
JM = 3n + 4
LM = 2n-12
Therefore; since the perimeter is the sum of the lengths of all the sides;
= n + n+7 + 3n + 4 + 2n -12 = 90
= 7n - 1 = 90
7n = 91
n = 91/7
n = 13 cm
Hence; KL = 13 cm