mohon bantuannya kuy susah banget nih

Keliling lingkaran = 2πr
jari-jari (r) = 3,5 cm
π = 22/7
K = 2 × 22/7 × 3,5
= 22 cm
panjang busur AB = < AOB / 360° × K lingkaran
= 120°/360 × 22
= 1/3 × 22
= 7,33 cm