Respuesta :

The size of the third angle is 65°.

All interior angles in a triangle must equal to 180°.

So, if 1st and 2nd angle is 115°, then, the 3rd angle would be equal to the difference of 180° and 115°.

3rd angle = 180° - 115° = 65°
65
Because a triangles angle all add up to 180
If 2=115
You do- 180-115= 65