Answer:
x =12.6
Step-by-step explanation:
The quadrilateral has 2 identical triangles.
so the area of the triangle is 104/2 = 52
given x is the red vertical line, so x/2 is used to calculate area of triangle
Area of triangle = 16.4(x/2)/2
16.4(x/2)/2 = 52
4.1x = 52
x = 12.6
Hope this helps