Two sides are given, either side of a vertical angle. So, the angles are the same. If the sides are proportional, the similarity will be by SAS (two sides, either side of an angle).
The ratios of short to long sides are ...
39/52 = (3·13)/(4·13) = 3/4
63/84 = (3·21)/(4·21) = 3/4
The sides are proportional and the angle between them is congruent, so ...
