Let the width of the rectangular deck be = x feet
The length is 6 feet more than the width so length is = x+6 feet
Let us assume that a total 3 feet is increased (1.5 feet on both ends)
As Hakeem decided to increase both dimensions by 3 feet, this means 1.5 feet is increased on both sides of the deck. So, length and width increases by 3 feet each.
Hence, new length is = x+6+3 = x+9 feet
New width is = x+3 feet
So new area = length*width
D =

=

=
square feet
Hence, option A is correct.