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Let u be the Jamie slower rate, in miles per hour (mph).
Then her faster rate is (u+24) mph.
Time at slower rate is hours.
Time at faster rate is hours.
The time for the two-way journey is the sum of these values, which gives you an equation
+ = 16 hours.
The setup is done.
To solve the equation, multiply both sides by u*(u+24). You will get
560*(u+24) + 560u = 16u*(u+24).
Simplify and solve this quadratic equation to get the answer u = 60 mph.
Answer. The slower speed was 60 mph. The faster speed was 60+24 = 84.
Solved.