I hope this helps so what but from my understanding. You could just find the hypotenuse from pythagorean therom and for that triangle, it is 17. Subtract 7.2 from 17 to recieve 9.8
You can also think about it logically for a sec. (if figure is drawn to scale)There is no way that length seems to be even close to 12.5. And the line seems about 65%ish of the hypotenuse.