jim can bike 10mph. 50 divided by 2 is 25, meaning they bike 25 miles put together each hour. if tim bikes at 15mph for 2 hours, he bikes a total of 30 miles. if jim bikes at 10mph for 2 hours, he bikes for a total of 20 miles. 30+20=50. if tim goes 30 miles in 2 hours, and jim goes 20, that means tim goes 10 more miles than jim in 2 hours. that would be the same as 5 more miles in one hour, since 10 divided by 2 is 5. hope this helps! (:
