start by finding the area of the rectangle the formula for which is length * breadth => 8*12 = 96
now since the triangles are equivalent based on the measurements, find the area of one and multiply it by 2
the formula for the area of a right angled triangle is (base * height)/2 => (3*12)/2 = 36/2 = 18
18*2 = 36
now add the triangles and the rectangle => 96 + 36 = 132 inches^2