SOLUTION: jacky was riding her new bike on the playground with other children.everyone was riding a bicycle or A tricycle.if jacky counted 12 WHEELS NOT INCLUDING HER OWN. HOW MANY KIDS WER

Let "b" be the number of bicycles and "t" be the number of tricycles, NOT COUNTING Jacky's bike.


Then from the condition, you have this equation


    2b + 3t = 12,      (1)      (counting wheels).


Thus you have one equation for 2 unknowns.
But you have, in addition, a restriction that the solution must be in INTEGER NON-NEGATIVE numbers.


It is very serious restriction, and in your case it provides a unique solution.


With this restriction, equation (1) has these and only these soLutions


    a      b
-------------------

    0       4

    3       2

    6       0


Now, from the condition, it is NATURALLY to assume that  a > 0  and  b > 0.


Then you have ONLY ONE solution  a= 3,  b= 2.


So, there are 3 bicycles and 2 tricycles, not counting Jacky's bike.


In this way, you get the ANSWER :


    there are 3 + 2 = 5 children on the playground, non counting Jacky herself.

    Or 5+1 = 6, counting Jacky.


The problem is solved.