Short Answer ? = 8
Remark
The bisector of an angle divides the line it is connected to in the same ratio as the ratio of the sides creating the angle containing the bisector.
Ratio
10 / x = 15/12 Cross multiply
10*12 = 15 * x Combine the left side
120 = 15 x Divide both sides by 15
120/15 = x
x = 8 <<<<< << Answer
