To find the missing length, we must first find the conversion for both of the side lengths (as in, the entire length). So, if we add 190+170, we get 360. 612/360=1.7, and 1.7 is our conversion factor. Now, if we multiply the adjacent side of the missing side length by 1.7 (which is 190), we can find the missing length. Thus, we find the answer is 323.
