A line adds up to equal 180 degrees. And adjacent angles also add to equal 180 since they share a side on a line. So add them together and make them equal 180
9x - 7 + 8.5x + 4 = 180
17.5x - 3 = 180
17.5x = 183
x = 10.5
The equation to find out the volume in this case is V=x*x*2x, or V=2x^3. Use this we can get that the volumes would be 16, 54, 128, and 250.