# A homeowner plots her house and yard on a computer. She determines that the circle that defines the part of the front yard that gets watered by the sprinkler is (x - 9)^2 + (y + 11)^2 = 16. What is the diameter of the circular area that gets wet?

I think $8 m$.
If i got the idea right you get, from your equation (of a circle in the form ${\left(x - h\right)}^{2} + {\left(y - k\right)}^{2} = {r}^{2}$), a circle of radius $r = \sqrt{16} = 4$ correspondent to a diameter of 2r=2×4=8. I think you may have meters as unit.