To find the shaded area, you need to find the area of the rectangle, and subtract the areas for the four triangles
Rectangle: A=l*w
A=18*8
A=144
Triangle: I am going to find the area of one triangle and multiply by 4 after since there are 4 triangles
A=1/2*b*h
A=1/2*4*4
A=2*4
A=8
Since there are four triangles, we do 8*4 to get 32
The we do the area of the rectangle minus the area of the triangles to find the answer
144-32=112 square inches
Hope this helps