Area of the modest sized house that is given in the question is = 155 m^2
Now, we already know that
1 meter = 10 decimeter
So
1 m^2 = 10^2 square decimeter
155 m^2 = 155 x (10)^2 square decimeter
= 155 x 100 square decimeter
= 15500 square decimeter
So the area of the house in question in decimeter square is 15500 decimeter square.