Answer: Yes
Explanation:
A supplementary triangle has sides adding up to 180°.
We have the side lengths 40, 60, and 80.
To find out if it is a supplementary triangle, we will add all the sides.
40 + 60 + 80 = 180
We get 180° as our answer when we add.
We got 180°, so the answer is yes, it can.
Best of Luck!