Question 47677
RT=R/2(T+5) OR RT=(RT+5R)/2 OR 2RT=RT+5R DIVIDING ALL TERMS BY R WE GET 

2T=T+5 OR T=5 & RT=300 OR R*5=300 OR R=300/5 OR R=60 MPH FOR THE CAR

300/60=5 HOURS 300/30=10 HOURS THUS 10-5=5 HOURS DIFFERENCE.