500 chairs in 11 rows, how much in ecach row?

The equation respenting the left table is

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?

1. find the area of the unshaded square 2. find the area of the large square 3. what is the area of the frame represented by the shaded region show