Question 1210391
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The sum of two numbers is 21. Five times the first number added to 2 times the second number is 66. Find the numbers.
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        I will show here how to solve this problem  MENTALLY,  without using equations.



<pre>
It is clear that we can re-formulate the problem  {{{highlight(highlight(EQUIVALENTLY))}}}  this way:

      Two  times the first number added to 2 times the second number is 42. 
      Five times the first number added to 2 times the second number is 66. Find the numbers


Looking in these two lines, your brain may conclude that three times (3 = 5-2) the first number is 
the difference 66-42 = 24.

Hence, first number is 24/3 = 8.

Then the second number is 21-8 = 13.


<U>ANSWER</U>.  First number is 8.  Second number is 13.
</pre>

Solved MENTALLY, without using equations.