He bikes 15 miles which is 10 times more than he swims. He runs 9 miles which is half of what he bikes 15/2=7.5. Plus the addition 1.5 miles which is 9. He swims .10 of what he bikes which is 15x.10 which is 1.5 . So he swims 1.5 miles.
Bikes = 15 miles Run= 9 miles Swim= 1.5 miles
Add all of them and you get 25.5 which the total amount of miles for his training that day.