The Triangle Angle Sum Theorem states that the sum of the angles in a triangle is always 180 degrees. In your triangle, you have the following angles:
- Angle A = 120 degrees
- Angle B = 34 degrees
- Angle C = ? (This is the angle we want to find)
According to the theorem:
\[ \text{Angle A} + \text{Angle B} + \text{Angle C} = 180^\circ \]
Plugging in the values we know:
\[ 120^\circ + 34^\circ + \text{Angle C} = 180^\circ \]
Now, combine the known angles:
\[ 154^\circ + \text{Angle C} = 180^\circ \]
To find Angle C, subtract 154 degrees from 180 degrees:
\[ \text{Angle C} = 180^\circ - 154^\circ = 26^\circ \]
Thus, the measure of the third angle (Angle C) is 26 degrees.