Question 1205185
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x = Ted's speed
x-75 = Justina's speed
Each speed is in meters per minute.


For Ted,
distance = rate*time
distance = (x meters per min)*(25 min)
distance = 25x


Now find the distance Justina traveled in the same 25 minute time frame.
distance = rate*time
distance = (x-75)*(25)
distance = 25(x-75)
distance = 25x-1875


Ted ran 25x meters which is the full track.
Justina ran 25x-1875 meters (i.e. 1875 meters less than a full track). Her distance is 5/8 of Ted's distance.


So,
Justina's distance = (5/8)*(Ted's distance)
25x-1875 = (5/8)*(25x)
8(25x-1875) = 5(25x)
200x - 15000 = 125x
200x-125x = 15000
75x = 15000
x = 15000/75
x = 200


200 meters per minute might sound like a lot, but it converts to roughly 7.456 mph, which is a typical average running speed. 
Sprinting speeds will likely exceed this, but keep in mind that we're talking about an overall average over the course of 25 minutes.
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