Answer:
3.33 meters per second
Explanation:
you must find the total time that Mr. B spent to complete the swim and bike.
Information:
0h 25' 10'' ---------> Swim
1h 30' 50'' ---------> Bike

he spent 1h 55' 60'', this is 1h 56'.
now you must substract this time from the record time to find the time alloted to run:
first you convert both times into minutes:

now substracting:

so he must travel 10 km in 50 minutes, that is:
speed = distance/time

1 km is equal to 1000 meters and 1 minute is equal to 60 seconds.

so Mr.B's speed must be 3.33 meters/sec