Mr.chen drove 23 miles south from where he started. 3.25×50=162.5 is what you have to do first because it said that he drove north for 3.25 hours and each hour he drives for 50 miles. Then you have to subtract 162.5 from 185.5 so that you get how far he drove from where he started. 185.5 - 162.5= 23. So he drove 23 miles south from where he started. I hope this helps.