Question 761799
12x=15(x-1)


12x=15x-15


12x-15x=-15


-3x=-15


x=(-15)/(-3)


x=5


So 5 hours total will pass by, but for you, 5-1 = 4 hours pass by (since she got the 1 hr head start). So it will take you 4 hours to catch up to her (after you start riding).