Answer:
Autumn walks T hrs = T * 6 km /hr
Spring rides 45 km/ 15 km / hr = 3 hr time for Spring to ride 45 km
3 hr + 1 hr = 4 hr time before Spring starts back
T * 6 + (T - 4) * 15 = 45 Autumn starts back at T - 4 hrs
(6 + 15) T - 60 = 45
21 T = 105
T = 5 hrs
Autumn travel 5 * 6 = 30 km
Spring travels 1 * 15 = 15 km
Total distance traveled = 45 km
Meeting place is 15 km from B