Answer:
AC = 6 cm
Explanation:
First, realize that these are two identical triangles. We just have to use the pythaogrean theorem on one side to find AD or DC, then multiply that by 2 to get AC.
a^2 + b^2 = c^2
8^2 + b^2 = 10^2
64 + b^2 = 100
100 - 64 = b^2
b^2 = 36
b = 6