In an isosceles triangle ABC (AC-base), angle B is 3 times greater than angle C. What is the major angle of this triangle?

Let the value of the angle ACB be equal to X0, then, by condition, the value of the angle ABC = 3 * X0.

Since the triangle ABC is isosceles, then its angles at the base of the AC are equal, then the angle BAC = BCA = X0.

The sum of the interior angles of a triangle is 180, then:

(X + X + 3 * X) = 180.

5 * X = 180.

X = 180/5 = 360.

Then the angle ABC = 3 * 36 = 108.

Answer: The large angle of the triangle is 108.