How in the holy hell do i do this ?

When you add the 18N to the 16s, you get 2N.  So the displacement is really the combination of 2N and 10E.  Its length is the square root of (2^2 + 10^2) ... that's the square root of 104.  Its direction is a little bit north of due east. (actually 11.3° north of due east)

not moving. pos accel,