Know these 2 properties -
1] A centroid is a point inside a triangle where all three medians coincide.

2] A centroid also divides a median in the ratio of 2:1

Basically F is the point of centroid of the triangle

Which also means F divides $\overline{DB}$ and $\overline{CE}$ in a ratio of 2:1

$\frac{\overline{BF}}{\overline{FD}} = \frac{\overline{CF}}{\overline{FE}} = \frac{2}{1}$

$\overline{FD}$ = 15

which means $\overline{BF} = 2*\overline{FD} = 2*15$ = 30

If you are confused my BF/FD and not FD/BF, so basically the centroid is farther away from the vertex point than from the point of intersection of median with a side.