In a triangle ABC AC = BC. The outside angle at apex B is 154∘. Find corner C.

Since AC = BC, then triangle ABC is isosceles, then angle ABC = angle BAC.
Since the outside angle of the ABC angle is 154, the ABC angle = 180 – 154 = 26 degrees.
Since the sum of the angles of a triangle is 180 degrees, then
angle ABC + angle BAC + angle ACB = 180
angle ACB = 180 – 26 – 26 = 128 degrees.
Answer: 128 degrees.

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