A triangle's angle measures add up to 180°.
67 + 90 = 157
180 - 157 = 23
The last angle measure is 23°.
The longer the side length, the larger the angle opposite it is. And vice versa. The shorter the side length, the smaller the angle opposite it is.
Side Length: ∠ Measure Opposite Side:
5 in 23°
12 in 67°
13 in 90°