The solution does not focus first on the numbers and simply write the answer, 15, but instead on the method, the process, by which the answer is obtained. The process forms a bridge between the exercises done to learn arithmetic operations and the mathematical methods needed to solve problems reliably.
Forming this bridge well before the fifth grade is essential to future success in using and appreciating mathematics.
Simple problems are excellent for forming reliable problem solving skills. This is accomplished by understanding the process by which problems are solved. The following example further illustrates the problem solving process. The above example is a sub problem of this problem.
One can not communicate well with the written or spoken word if the grammar of the language is not used. In the same way one can not communicate effectively, with others and with one's self, through problem solving without using the grammar of problem solving.