If the triangles are similar then the angles in both are equal. Let's look at each set individually:
(1) Triangle 1: 25°, 35° Triangle 2: 25°, 120° Now it may be hard to tell if the triangles are similar at the moment so we must calculate the third angle in each triangle (The angles in a triangle add up to 180°, therefor the missing angle = 180 - (given angle 1 + given angle 2) Triangle 1: 180 - (25 + 35) = 120° Triangle 2: 180 - (25 + 120) = 35°
Now writing out the set of angles again we have: Triangle 1: 25°, 35°, 120° Triangle 2: 25°, 120°, 35°
So in fact Triangle 1 and 2 are similar.
Now we can repeat this process for (2) - (5):
(2) Triangle 1: 100°, 60°, 20° Triangle 2: 100°, 20°, 60° This pair is also similar
(3) Triangle 1: 90°, 45°, 45° Triangle 2: 45°, 40°, 95° This pair is not similar
(4) Triangle 1: 37°, 63°, 80° Triangle 2: 63°, 107°, 10° This pair is not similar
(5) Triangle 1: 90°, 20°, 70° Triangle 2: 20°, 90°, 70° This pair is similar
