Arectangular stained glass window is made up of identical triangular parts as pictured below.

Hence, the area of shaded region is:

72 square inches.

We have to find the area of the shaded region i.e. we have to find the area of a triangle.

Clearly the shaded triangle is in the shape of a right triangle.

we will firstly find the dimension of the triangle in order to find it's area.

Clearly the base(b) of a triangle is 36/4= 9 inches.

( since the side of the rectangle of length 36 inches is divided into 4 equal parts)

similarly the height(h) of the right triangle is:

48/3=16 inches.

( since the side of rectangle of measure 48 inches is divided into 3 equal parts)

Hence, the area of triangle is calculated as:

Hence, the area of shaded region is:

72 square inches.

ian gonna lie that is way to much