The length of GM is 16. It is obtained from the right triangle KMI, altitude IG is drawn to hypotenuse KM and KG = 9 and IG= 12.
Explanation:
The given is,
 Right triangle KMI
 KG = 9
 IG= 12
Step:1
 From the triangle KMI,
  90° = ∅
 + ∅
.................................(1)
 From the triangle KGI,
 Trignometric ratio,
  tan ∅
 = 
.................................(2)
 Where, Opp = 9
 Adj = 12
 Equation (2) becomes,
 tan ∅
 = 

 = 0.75
 ∅
 = 
 0.75
  ∅
 = 36.87°
 From the equation (1),
 ∅
 = 90° - ∅

 = 90° - 36.87°
  ∅
 = 53.13°
 From the triangle IGM,
 tan ∅
 = 
..........................(3)
 Where, Opp = GM
 Adj = 12
 ∅
 = 53.13°
 Equation (2) becomes,
 tan 53.13° = 

 GM = (1.333)(12)
 = 15.999
  GM ≅ 16
Result:
 The length of GM is 16. It is obtained from the right triangle KMI, altitude IG is drawn to hypotenuse KM and KG = 9 and IG= 12.