We could determine how far he walks by multiplying how far he walks each day by 5. We could write it like this,
walk 5 days = walk each day × 5
Now input the numbers
walk 5 days = walk each day × 5
walk 5 days = 5/8 × 5
walk 5 days = 25/8
walk 5 days = 3 1/8 (mixed number)
walk 5 days = 3.125 (decimal)
Mathew walks 3 1/8 miles or 3.125 miles in 5 days