Be nice if we were sure of the question. I will guess that you want the hypotenuse.
c^2 = a^2 + b^2
a = 6 km
b = 6 km
c^2 = 36 + 36
c^2 = 72
c = sqrt(72)
c = sqrt(9 * 8)
c = 3*sqrt(8)
c = 3 * 2.83
c = 8.49
100 is the y intercept so its graohed at (0,100)(y-axis) and it goes up every 1/55
The answer is D. 9(y + 3) and 27 + 9y because 9(y + 3) when expanded is 9y + 27. I hope this helps!