Answer:
scale factor = 1/2
Explanation:
for AC: 4 + 4 = 8
8 is the AC of the red triangle
4 is the AC of the blue triangle
to get from 8 to 4, we divide by 2 or multiply by 1/2 (they mean the same thing)
10 is the CB of the red triangle
5 is the CB of the blue triangle
to get from 10 to 5, we divide by 2 or multiply by 1/2