Answer
(-5m)i + (8m)j
Work Step by Step
In order to find the position vector of a particle, you need to find it's displacement from the origin (0,0,0). In this question, you are told that the watermelon seed has the coordinates x=(-5m), j = 8m and z=0m. Since x corresponds to i, y corresponds to j and z corresponds to k, these can be changed to i = -5m, j = 8m and k=0m. Writing these in unit vector notation we have:
(-5m)i + (8m)j + (0m)k
Since the k component is zero, we can write it merely as
(-5m)i + (8m)j
