tolong jawab ya penting besok dikumpul? soal no1 dan 3

1. DE/AB = CD / CA
12/18 = 8/CA
CA = 12cm
DA= 12-8=4c

3a. 6/9 = 4/a
A=6

3b. 8/12 = b/b+4 *kali Silang*
3b = 2b + 8
B = 8

3c. 6/9 = 8/8+c
12 = 8+c
C = 4

3d. 4/12 = d/6+d
3d = 6+d
2d= 6 d = 3

*Moga bener & membantu*