bntu donk ni pakai cara no 8 smpai 11

No 8 :
Cari sudut acb
= 180 - (72+51)
= 180 - 123
= 57°
Jadi sudut bcf
180 - 57 = 123°
No 9 :
pakai pytaghoras
s^2 = 12^2 + 5^2
= 144 + 25
= 169
s = 13 cm
Keliling ∆ = 13 + 12 + 5
= 30 cm^2
No 11 :
Luas ∆ = 1/2 at
63 = 1/2 (18) t
63 = 9t
7 cm = t