Answer:
Steven is faster than Michelle by covering 0.64 meters more per second than that of Michelle.
Step-by-step explanation:
Given:
Steven swam 200 m in 25.7 seconds while Michelle finished in 28 seconds.
So, speed of Steven is, 
Speed of Michelle is, 
Now, to find how much faster did Steven swim than Michelle, we need to get the difference between their speeds.
Speed of Steven - Speed of Michelle


So, Steven is faster than Michelle by covering 0.64 meters more per second than that of Michelle.