minta jawab yg bener y?oke nih 7,8dan9 tolong plis☺

180°=20°+(5X+5)°
180°-25°=5X
155°=5X
X=31

<A=180-(<B+<C)
<A= 180-((3(31)-15)+20
   =180-98
   =82°

7) A:B:C = 3:4:5
A+B+C=12
A = 3 per 12 × 180° = 45°
B = 4 per 12 × 180° = 60°
C = 5 per 12 × 180° = 75°