.
The condition missed the following:
1. Did they start from one common point ?
2. Did they start simultaneously ?
3. Do they move in the same or opposite directions ?
For introductory lessons on Travel & Distance 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.
They are written specially for you.
Learn from there on how to formulate these problems.
Happy learning !
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Comment from student: Yes they start the same time and travel in the same direction
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My response : OK.
Then the solution can be implemented in two lines :
The separation rate is then (10-4) = 6 miles per hour.
Hence, they will be 24 miles apart in 
= 4 hours. ANSWER
Or the formal Algebra solution :
Let "t" be the time when they be 24 miles apart.
At that time Kevin will cover the distance of 10*t miles, while Stanley will cover 4*t miles.
The distance difference should be 24 miles; it gives you an equation
10t - 4t = 24 miles,
6t = 24 miles
t = = 4 hours. ANSWER
Thus I showed you two ways the problem can be solved.
