Supermarket parking Problem form Italy Comenius Why Maths

1. Example 1 (from Italy)
We have to build a supermarket and its parking (look at the image). x is
smaller than the half of square's side. How must x measure to make a parking
19332m2 large?
Solution:
150 2  19332  x150  x   x150  2 x 
3168  150 x  x 2  150 x  2 x 2
3168  3x 2  300 x
x 2  100 x  1056  0
x  50  2500  1056  50  38  x1  88 not acceptable (because of the
constraints)
x2  12
So the supermarket side has to be 12m long.