What is the equation of the line that passes through points (-3,0.5) and (3,-0.5)

If you insert both points into the standard form y=mx+b you receive
I:0.5=-3m+b
II:-0.5=3m+b
subtraction of II from I to eliminate b:
0.5-(-0.5)=-3m+b-3m-b
1=-6m
m=-1/6

insert this in I again:
0.5=-3m+b
0.5=-3*(-1/6)+b
0.5=1/2+b
0=b
-> y=(-1/6)x

4hours and 40 mins she would be 120 meters high