Answer :
[tex]3,200ft^2[/tex]
Explanation:
Since each of her steps is equivalent to 2 feet
=> 1 step = 2 ft
==> 20 steps = 2 * 20 = 40 feet
==> 40 steps = 2 * 40 = 80 feet
The square feet of the backyard is equal to width * height
[tex]40\cdot80=3,200ft^2[/tex]