So first (3 1/2) equals to 3+1/2 which is 7/2, same for(2 1/3), 2+1/3=7/3. It's asking for speed in laps per minute, so like how many labs did she swim per minute, which is labs over time——(7/2)/(7/3)=(7/2)*(3/7)=3/2. So she swam 3/2 labs per minute.