tolong jawab sama caranya nanti saya jadi in jawaban terbaik

1. DE : AE = BC : AC
9 : (8+a) = 6 : 8 ( kali silang )
6 ( 8+a ) = 9 × 8
48 + 6a = 72
6a = 72 - 48
6a = 24
a = 24 ÷ 6
a = 4

2. AE : AD = AC : AB
12 : (5+b) = 8 : b ( Kali Silang )
8 (5+b) = 12b
40 + 8b = 12b
40 = 12b - 8b
40 = 4b
b = 40 ÷ 4
b = 10