<h3>
Answer: 216 square inches</h3>
==============================================================
Explanation:
Let's focus on the upper left triangle. This triangle is a right triangle because the diagonals of any rhombus are always perpendicular.
Use the pythagorean theorem to find the missing leg of this triangle

We'll consider this the height. The base is 12.
area of triangle = base*height/2
area = 12*9/2
area = 108/2
area = 54
This represents the area of the upper left triangle.
Because the diagonals of a rhombus bisect each other, this leads to the four triangles shown being identical copies of one another.
So we simply need to multiply that result of 54 by 4 to get the total area of the rhombus.
4*54 = 216 square inches is the area of the rhombus.