Answer:
AC = 36
Step-by-step explanation:
since these triangles are similar, we can use the triangle similitary theorem. This means that the sides are proportional to each other.
ef/bc = 5/45 (1/9) = ed/ba = 2/18 (1/9)
we can see the sides are in a ratio of 1:9, and plug it in the proportion
df/ac = 1/9
4/ac = 1/9
cross multiply and we get that ac = 36
