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Let "x" be the speed of the fastest cyclist in miles per hour.
Then the speed of the slower cyclist is (x-4) miles per hour.
In 3 hour the fastest cyclist will cover 3x miles, while the slower will cover 3*(x-4) miles.
The sum of distances is 108 miles. It gives you an equation
3x + 3*(x-4) = 108.
Simplify and solve for x:
3x + 3x - 12 = 108,
6x = 108 + 12 ====> 6x = 120 ====> x = 20.
Answer. The fastest cyclist speed is 20 mph. The slower cyclist speed is 20-4 = 16 mph.
For many other similar solved problems see the lessons
- Travel and Distance problems
- Travel and Distance problems for two bodies moving in opposite directions
- Travel and Distance problems for two bodies moving in the same direction (catching up)
in this site.