Answer:
138°
235°
240°
Explanation:
The first situation shows a straight angle, so the smaller angles that make it up should be supplementary. That means that their measures add up to 180°. My work for this first situation is shown below:
n + 42° = 180°
n + 42° - 42° = 180° - 42°
n = 138°
Now, let's look at the second situation. This one's pretty simple. It's just asking us to add up the measures of all the angles are given, so all we have to do is some addition, shown below:
23° + 40° + 92° + 80° = 235°
Finally, we're at the last situation. This situation shows a full angle, so the smaller angles that make it up should add up to 360°, since this is the amount of degrees in a full circle. Again, if we know the measure of one of these angles, we should be able to find the measure of the other one. See my work below:
n + 120° = 360°
n + 120° - 120° = 360° - 120°
n = 240°
And there are all your answers! Let me know if you need further clarification on all that. :)