Three interior angles of a quadrilateral have measures of 100∘, 120∘,100∘, 120∘, and 80∘80∘. Find the fourth angle measure.?

　
I'm not sure what's going on, but each value seems to appear twice.
I'll assume angles are: 100°, 120°, and 80°.

Did you know that sum of angles in a quadrilateral is 360°?
So just find an angle that when added to the other 3 will give 360°.

360−100−120−80 = 60

Fourth angle = 60°

There are FOUR angles in a quadrilateral.

The interior angles in a quadrilateral add up to 360°
S = (4 - 2) * 180 = 360°

Let x be the fourth angle.
100 + 120 + 80 + x = 360
300 + x = 360
x = 60°

Answer:
60°