tolong bantuin aku kak pliss

A+B+C = 180
70+60+C = 180
130+C=180
C=50
A.) C3=C4
C+C3+C4=180
50+2C=180
2C=130
Jadi C3+C4=130
B.) B1=B2
  B1+B2=60
  B2=30
C.) D+B2+(C+C3)=180
      D+30+125=180
      D+155=180
      D=25

Diketahui
Sudut
B1 = B2
C3 = C4
A = 70°
B = 60°

jawab
(a)
C3 + C4 + (180 - A - B) = 180
C3 + C4 + ( 180 - 70 - 60) = 180
C3 + C4 + 50° = 180
2 x C3 = 180 - 50
2 x C3 = 130
C3 = 130 / 2
C3 = 65°
C4 = C3 = 65°

C3 + C4 = 65 + 65 = 130°

(b)
B1 = B2
2 x B1 = B
2 x B1 = 60°
B1 = 60° / 2
B1 = 30°
B2 = B1 = 30°
B2 = 30°

(c)
D = 180 - B2 - C3 - (180 - A - B)
D = 180 - 30 - 65 - (180 - 70 - 60)
D = 180 - 30 - 65 - 50
D = 35°