What exactly is AG? I've been lost

Answer:
AG is the line that has been shown in the image.
I believe AG = 10
Answer:
AG = 10
Step-by-step explanation:
On each median the distance from the vertex to the centroid is twice as long as the distance from the centroid to the midpoint , then
AG = [tex]\frac{2}{3}[/tex] × AE = [tex]\frac{2}{3}[/tex] × 15 = 10