I am checking to see if I understand this problem correctly.

Find the magnitude of the vector u = QP--> with Q = (6, 6) and P= (-3, 8)

The arrow indicates the directed line segment.

-3 - 6 = -9

8 - 6 = 2

||v|| = sqrt( (-9)^2 + 2^2 ) = sqrt(85) = 9.2195