so what is happening is you need to find out the unknown length. Because the side EH is similar to side AD ( its similar because the shape has been rotated) you can put them over one another. Now you need to have another equal side to complete the problem so you use the other set of sides. To make this problem easier we should make the side EH into a variable. to make it AD over X. now the problem is BC over FG is = to AD over X. The next step is to simplify into numbers because it is hard to just work with letters. So now the problem is 12 over 30 = 16 over X. The next step is to cross multiply so the problem is 12X = 30 x 16. Now we can simplify this equation to 12X= 480. the next thing you want to do is to divide 240/12 because you need to get X by its self. Resulting in (Remember X stands for EH) EH = 40in.
