Question 1080137
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Your equation is

{{{24/r}}} = {{{16/(r-4)}}}.


Cross multiply:

24*(r-4) = 16r,

24r - 96 = 16r  --->  24r - 16r = 96  ---->  8r = 96  --->  r = {{{96/8}}} = 12.


<U>Answer</U>. The speed during the first portion is 12 miles per hour
         and the speed during the rest of the trip was 12-4 = 8 mph.
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