bearing in mind that the centroid in a triangle cuts each of the three medians in a 2:1 ratio.
since we know that A C = 12, let's split it in a 2:1 ratio then, cleary from the picture the larger is F C, so F C : A F is on a 2:1 ratio.

Answer:
d = 
Step-by-step explanation:
The nth term of an arithmetic sequence is
= a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Given a₉ = 16 , then
- 12 + 8d = 16 ( add 12 to both sides )
8d = 28 ( divide both sides by 8 )
d =
= 