Mary and jerry are exercising on a track -mary is walking at a rate of 3 miles per hour -jerry starts jogging at a rate of 4 miles per hour after mary has been walking for 15 minutes -jerry jogs 2 miles as mary continues walking and they both stop at the same time enter the total distance, in miles, that mary walks around the track

Jerry stopped after reaching 2 miles, therefore with the rate of 4 miles per hour, Jerry had only consumed 30 minutes. The given said the two persons stopped at the same time, therefore Mary stopped walking after 30 minutes.

With Mary's rate of walk, 3 miles per hour, we can just convert it to minutes and find the distance she has covered after 30 minutes.

3 miles/ 60 minutes, multiplying both numerator and denominator by 1/2, we will have 1.5 miles/30 minutes. Therefore, Mary has covered a distance of 1.5 miles around the track after the walk.