First you have to look at the way the shape is named based on order in each other. ABCD is congruent to GJIH. This means A will be congruent to G, and J will be congruent to B and so on. Same goes with side lengths, so that mean segment GH is congruent to AD based on the order of the name.
So x/3=9
You multiply by 3 on both sides to get x by itself.
So now your answer is x=27
