Answer:
y = 30
Step-by-step explanation:
the 2 marked sides are congruent, thus the triangle is isosceles with the 2 base angles being congruent, both (y + 24)°
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
(4y - 12)° is an exterior angle of the triangle , then
4y - 12 = y + 24 + y + 24
4y - 12 = 2y + 48 ( subtract 2y from both sides )
2y - 12 = 48 ( add 12 to both sides )
2y = 60 ( divide both sides by 2 )
y = 30
