Let us set the length to=L,
Since Abigail has done 3/4L=6,
Then we just divide both sides by 6, and we get:
L=6/ (3/4), which is the same as: 6 X 4/3(notice that I flipped 3/4 upside down),
Then we have:( 6 X 4)/3=24/3=8 Miles, which is total length of the track.