I dont think you posted the picture.
So, let's first find the slope of the second question:
Our second equation has a slope of one half, so we know that a line perpendicular to it will have the negative reciprocal slope of that, so -2. We have this now as our equation:

We are given the point (3,-6), so let's plug the x and y in and find our b:

Since our b is 0, our equation is simply:

Slope = Rise / Run
Road grade is vertical increase ( Rise ) divided by the horizontal increase ( Run ).
The boat ramp:
Road Grade (B) = 6 ft / 36 ft = 1/6 = 0.167
The road:
Road Grade (R) = 12 % = 0.12
0.167 > 0.12
Answer: The boat ramp is steeper.