Miguel's 1 1/2 times can be written out as 1.5 because 1/2 is equal to 0.5,
To work out the distance you need to times Abby's miles by 1.5. Another way of doing this is by dividing Abby's miles by 2, working out the 0.5, and then adding her original miles, adding on the 1 to make 1.5.
2 1/3 / 2 = 1 1/6
1 1/6 + 2 1/3 = 3 3/6 = 3.5 miles
Hope this helps! :)