Let x be the required height-to-length ratio and y be the actual height-to-length ratio of the ramp.
We know that x = 1/12 and the height of the ramp is h. The length of the ramp would be l, which we can solve for using the given ratio:
x = h/l (required height-to-length ratio)
1/12 = 2.2/l (actual height-to-length ratio)
To create a proportion, we set the two ratios equal to each other:
x = 1/12 = h/l = y
So the proportion is:
1/12 = h/l = y