To figure this out, first, figure out the area of the whole yard:
The equation for area is length*width.
So, 60 ft long*40 ft wide=2400 square feet.
But the flower bed will not be fertilized, so we subtract that out:
Again, area of the flower bed is length*width.
20 ft long*4 ft wide=80 square feet.
Then, just subtract the area of the flower bed from the total area:
2400 square feet-80 square feet=2320 square feet.
So, 2320 square feet of Clark's yard will be fertilized.