Answer:
28 laps
Explanation:
Let laps swam by Jackie be J, and laps swam by Ronnie be R.
"For every 3 laps that Jackie swims Ronnie swims 2 laps":

"they swam a combined total of 70 laps ":

Now, solving for J of the first equation and putting that into the 2nd equation, we can know R:

So, Ronnie swam 28 laps.