Trying to find the missing segment to the triangle in the attached image.

Answer:
25
Step-by-step explanation:
The Side Splitter Theorem says that if a line intersects two sides of a triangle and is parallel to the third side of the triangle, it divides those two sides proportionally. Therefore:
6/15 = 10/?
6*? = 10*15
? = 10*15/6
? = 25