y^2 / 6x^2 + 2x + z
I'm not that certain that this is it, but my best guess.
I believe it is quadratic parent function, i apologize if I'm incorrect.
15 is the answer I think because that is the Greatest Common Factor of all three of them.
I hope this helps!
Well 500 mm = 50 cm so if you add both segments together you will get a 50+30=80cm segment