i am bad at this types of questions but will give you what i would write of the question if i had it
If his run is 16/8 miles per day, 8/10 of the run is 16/8×8/10= 2×8/10
= 16/10
= 1.6
but... i am not sure if the question requires yoi to add the miles from the pervious day as the break was only stated in the second day. If i were you, i will leave the answer as 1.6 miles.