The correct method to find the sum of the interior angles of a triangle is:
Option A: (n−2)⋅180° (Here, n is the number of sides of the triangle, which is 3. So the sum of the interior angles of a triangle is (3-2)⋅180° = 180°.)
Option B: ∠1 + ∠2 + ∠3 (This expresses the sum of the angles as the addition of those angles, which also equals 180° for a triangle.)
Since both options are correct methods to arrive at the sum of the interior angles of a triangle, the answer is:
3 for both Option A and Option B.