Answer:
y = 14
Step-by-step explanation:
Since AC = BC then the triangle is isosceles and the base angles are congruent, that is
∠A = ∠B = 50°, thus
∠C = 180 - (50 + 50) ← sum of angles in Δ = 180°
= 180 - 100 = 80°, hence
5y + 10 = 80 ( subtract 10 from both sides )
5y = 70 ( divide both sides by 5 )
y = 14
