For part a:
Divide 300 (meters) by 2 (minutes). You'll get 150 (meters), or Joel's distance if he swims for 1 minute. Then you multiply that by five to find Joel's distance if he swims for 5 minutes (150 multiplied by 5). The product will be your answer.
For part b:
Divide 2400 (meters) by 4 (minutes). You'll get 600 (meters), or Joel's distance if he bikes for 1 (minute). Then, you multiply that by 16 to find Joel's distance if he bikes for 16 minutes (600 multiplied by 16). Add that answer to the answer you found in part a and you have the answer for part b.