Answer:
Angelina hiked 450 ft before the first stop.
Explanation:
She hiked along a 2250 foot mountain trail. 
She stopped 4 times, she rested and after that stopped 5 times. 
She walked the same distance between each stop. 
It means 5 stops and the same distance with each time. 
We need to calculate the distance between each stop. Total distance T = 2250 ft, and stops S = 5. 
We can isolate the distance of each Stop E from:
T = S*E
E = T/S = (2250 ft)/(5)
E = 450 ft.
Finally, She hiked 450 ft before the first stop.