need help w/ "Lois rode her bike at 10mph; on the way b

Can someone help me? I'm trying to explain how to do this question to my sister and I'm doing a horrible job. Maybe someone can explain it better than I can.

Lois rode her bike to visit a friend. She traveled at 10 mi/h. While she was there, it began to rain. Her friend drove her home in a car traveling at 25 mi/h. Lois took 1.5h longer to go to her friend's house than to return home. How many hours did it take Lois to ride to her friend's house?

Thanks for all your help.[/u]

Re: need help w/ "Lois rode her bike at 10mph; on the w

Let t = time taken @ 10mph; then time taken @ 25mph = t - 1.5 or t - 3/2

distance = speed * time
since distance is same:
10t = 25(t - 3/2) ; divide by 5 to simplify:
2t = 5(t - 3/2)
2t = 5t - 15/2 ; multiply by 2 to get rid of fraction:
4t = 10t - 15
6t = 15
t = 15/6 or 2.5 hours