Hello!
For this problem we are given that quadrilateral ABCD is congruent to quadrilateral GJIH, meaning that all sides and angle measures will be equivalent to its corresponding side.
This means that to find [tex]x[/tex], we can look at quadrilateral GJIH's corresponding side to quadrilateral ABCD's side AD, which is side GH, which has a value of 9.
This means that 9 should also be the side length of side AD, which we're given a value of [tex]x/3[/tex].
[tex]x/3=9[/tex]
Solve.
[tex]x=27[/tex]
Hope this helps!
