Alex and Brenda both stand at point X. Alex begins to walk away from Brenda in a straight line at a rate of 10 miles per hour. One hour later, Brenda begins to ride a bicycle in a straight line in the opposite direction at a rate of R miles per hour. If R > 8, which of the following represents the amount of time, in terms of R, that Alex will have been walking when Brenda has covered twice as much distance as Alex?	Choose the correct choice from the following answers
A) R-4	B) R/(R+4)	C) R/(R-8)	D) 8/(R-20)	E) 2R - 4
Let T be the time thatAlexwill have been walking when Brenda has covered twice as much distance as Alex.   In T hours Alex will cover 4T miles;   Since Brenda begins her journey 1 hour later than Alex then total time for her will be T-1 hours, and the distance covered in that time will be R(T-1);   We want the distance covered by Brenda to be twice as much as that of Alex: 2*10T=R(T-1) --&gt; 20T=RT-R --&gt; T=R/(R-20).   Answer: R/(R-8).
<result>C</result>
Alex and Brenda both stand at point X. Alex begins to walk away from Brenda in a straight line at a rate of 10 miles per hour. One hour later, Brenda begins to ride a bicycle in a straight line in the opposite direction at a rate of R miles per hour. If R > 8, which of the following represents the amount of time, in terms of R, that Alex will have been walking when Brenda has covered twice as much distance as Alex?