I will assume that line 4 bisect line x exactly in half. This means that if we solve the last side of the triangle like seen in the pic below we will know what half of line x isTo find the length of the last side of the triangle (let's call this y) you must use Pythagorean theorem
[tex]a^{2} +b^{2}=c^{2}[/tex]
a and b are the legs (the sides that form a perpendicular/right angle)
c is the hypotenuse (the side opposite the right angle)
In this case...
a = 4
b = y
c = 6
^^^Plug these numbers/variables into the theorem
[tex]4^{2} +y^{2} =6^{2}[/tex]
solve for y
16 + [tex]y^{2}[/tex] = 36
[tex]y^{2}[/tex] = 20
x = √20x ≈ 4.472^^^This is only half of x so if you double it then it will get you the full length of x4.472 * 2 = 8.9448.9 (D)Hope this helped!~Just a girl in love with Shawn Mendes