Answer:
the area of the whole rectangle =20cm×30cm
area of rectangle =600cm²
hieght of the triangle is equal to the breadth of the square.
area of triangle=1/2×base×height
area of triangle=1/2×30×20
area of triangle =300cm²
area of shaded region=area of rectangle-area of triangle
"""""" =600cm²-300cm²
area of shaded region =300cm²