I didn't understand this question on my practice quiz. Can someone please explain?

Answer:
x = 3.6
Step-by-step explanation:
the ray is an angle bisector and divides the opposite side into segments that are proportional to the other 2 sides , that is
[tex]\frac{6}{x}[/tex] = [tex]\frac{4}{6-x}[/tex] ( cross- multiply )
6(6 - x) = 4x
36 - 6x = 4x ( add 6x to both sides )
36 = 10x ( divide both sides by 10 )
3.6 = x