bantuin donk guys T-T

12^2 + 9^2 = √225 = 15 -> Panjang OA
Memakai Luas
1/2 x panjang x tinggi = 1/2 x 12 x 9 = 54
54 = 1/2 x OA x 1/2BC -> setengah BC
54 = 1/2 x 15 x 1/2BC
1/2BC = 7.2cm
Maka BC = 7.2 x 2 = 14.4cm

Semoga Membantu :]