Answer:
100 degrees
Step-by-step explanation:
The angles in a triangle must add to 180 degrees.
We know 2 of the angles, 60 and 20. We don't know the third, so we can call it x.
60, 20 and x added together must equal 180, or
60+20+x=180
Add 60 and 20
80+x=180
We are trying to find the third angle, or x. In order to do this, we have to get x by itself. 80 is being added onto x. To undo this, subtract 80 from both sides
80-80+x=180-80
x=100
So, the third angle is 100 degrees
