A centroid of triangle is a point where the three medians of the triangle meet. The point P is the midpoint of the line MN:
MP = PN
3 x - 4 = x + 4
3 x - x = 4 + 4
2 x = 8
x = 8 : 2 = 4
Line MS: MS = 2 x + 2 = 2 · 4 + 2 = 8 + 2 = 10
Then: SQ = MS : 2
SQ = 10 : 2
SQ = 5
Answer: B)