Ajogger ran 4 miles, decreased her speed by 1 mile per hour, and then ran another 5 miles. if her total jogging time was 2 1/20 hours, find her speed for each part of her run.

Let the speed of the joker initially be x mi/hr
after reduction, the new speed will be: (x-1) mi/hr
but
time=(distance)/(speed)
hence :
Total time taken will be:
4/x+5/(x+1)=41/20
solving for x we get:
x=21.585 mi/hr
thus the initial speed was 21.585 mi/hr after reduction the new speed was 20.585 mi/hr