Two vertical angles are never adjacent.
I hope this helps :)
The sum of the rational expression is
X=4
In the figure below
1) Using the theorem of similar triangles (ΔBXY and ΔBAC),

Where

Thus,

thus, BC = 7.5
2) BX = 9, BA = 15, BY = 15, YC = y
In the above diagram,

Thus, from the theorem of similar triangles,

solving for y, we have

thus, YC = 10.
Y^3 * y^5 = y^8. you add the exponents