Kak bantu ya tolong........

Kelas 8 Matematika
Bab Lingkaran

a] ∠AOB = 2 . ∠BCA
∠AOB = 2 . 25°
∠AOB = 50°

b] Segitiga ABO adalah segitiga sama kaki, karena AO = OB 
∠AOB + ∠OAB + ∠OBA = 180°
50° + 2 . ∠OAB = 180°
2 . ∠OAB = 180° - 50°
∠OAB = 130/2
∠OAB = 65°

c] ∠ABC = ∠OBA + ∠CBO
∠ABC = 65° + 15°
∠ABC = 80°

d] ∠BAC = 180° - ∠ABC - ∠BCA
∠BAC = 180° - 85° - 25°
∠BAC = 70°

Pelajaran : Matematika

Jawaban :
a.) sudut AOB = 2 x sudut BCA
= 2 x 25⁰
= 50⁰

b.) 2x + 50 = 180
2x = 130
x = 65°

c.) sudut ABC = sudut OBA + sudut CBO
= 65 + 15
= 80°

d.) Sudut BAC = 180° - 80° - 25°
= 75°