Approximately 144 miles. You have to use the pythagorean theorem. a^2+b^2=c^2.
120 and 80 will be the legs, a and b. 120^2 + 80^2 = c^2. 14400 + 6400 = 20800. Remember, c is squared, so to find the answer, you need to find the square root of 20800, which is 144.222051019. Therefore, c, the road between Hermansville and Melville, would be approximately 144 miles.