

The solution is started by responding to what is ASKED FOR: Find the age of David. This fundamental principle of reliable problem solving is included in
SureMath  the math software for 21st century problem
solving.
The problem statement provides information about David's age, thus giving a place to start the solution.
After solving the starting equation for David, the resulting equation ASKS FOR information about Jim's age and Tom's age.
These requests are "subproblems" of the main problem, therefore are shown indented in the solution. An organized presentation of a problem solution enhances communication between the problem solver and himself as well as with users of the solution.
When the requests made by the starting equation are satisfied, the problem solution is completed by substituting the information into the starting equation.
Copyright 1996. Howard C. McAllister