Let:
a = original area of the rectangular flower bed
y = enlarged area of the rectangular flower bed
The new area of the flower bed is:
y = x^2 + 11x +24 ft^2
y = (x+3) (x+8)
If the flower bed area is increased by 24 ft^2
y = a + 24 ft^2
y = x^2 +11x + 24
Therefore, the original area of the bed is x^2 +11.