To find which pair gives two of the three interior angles of a triangle such that the third angle is equal to one of the given angles, we need to recall that the sum of the interior angles of a triangle is always 180 degrees.
For each of the pairs, we will check if the sum of the two angles provided, when subtracted from 180 degrees, results in one of those two angles.
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Pair: 20°, 40°
- Sum = 20° + 40° = 60°
- Third angle = 180° - 60° = 120° (not equal to 20° or 40°)
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Pair: 30°, 60°
- Sum = 30° + 60° = 90°
- Third angle = 180° - 90° = 90° (not equal to 30° or 60°)
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Pair: 50°, 80°
- Sum = 50° + 80° = 130°
- Third angle = 180° - 130° = 50° (equal to 50°)
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Pair: 45°, 120°
- Sum = 45° + 120° = 165°
- Third angle = 180° - 165° = 15° (not equal to 45° or 120°)
Only the pair 50°, 80° results in a third angle that is equal to one of the given angles (specifically 50°).
Therefore, the answer is 50°, 80°.