The sum of all the exterior angles of a triangle is
Let the exterior angles of the triangle be x, y and z respectively.
Then by exterior angle property, interior angles of the triangle will be (180−x)∘, (180−y)∘, (180−z)∘
Using angle sum property of a triangle,
(180 - x) + (180 - y) + (180 - z) = 180
540 - (x + y + z) = 180
Therefore, x + y + z = 360∘