Answer:
y = 15
Explanation:
since AB and AC are congruent then Δ ABC is isosceles with base angles congruent, that is
∠ C = ∠ B = 25°
the sum of the 3 angles in a triangle = 180°
sum the 3 angles and equate to 180
∠ A + ∠ B + ∠ C = 180 , so
7y + 25 + 25 + 25 = 180
7y + 75 = 180 ( subtract 75 from both sides )
7y = 105 ( divide both sides by 7 )
y = 15