a. Since #ABCDE# and #GHJDF# are similar shapes, this implies that the angle of one point in one shape is equal to another angle of one point in the other shape. In this case, #/_H# is equivalent to #/_B# because they share the same relative point between the shapes. You can also approach this question by identifying that #H# is the second letter in the shape name. If you look at #B#, you will also notice that the second letter in the shape name is #B#.
b. Just like in part a, you are trying to find one relative value in one shape that is equal to the other shape. Look at the left side of the equation, you will notice that it is a ratio of sides. The goal is to match the left with the right side. The ratio is side #GH: DJ#. Notice that it is a ratio of the top right side to the bottom side of the shape. If you follow this format for shape #ABCDE#, you will notice that the top right side is #AB# and the bottom side is #DC#. Since the question is just asking for the denominator of the ratio, your answer is just #DC#.
