<PRE><B>Question 1210391</B>
&lt;br&gt;
Some of the tutors who have responded use a single variable to solve the problem.  Others use two variables to make two equations and then use substitution to solve the problem.&lt;br&gt;
Those are valid methods.  But with the problem worded the way it is, forming two equations in two unknowns and solving by elimination would seem to be the most direct approach.&lt;br&gt;
x = first number
y = second number&lt;br&gt;
(1) x+y = 21  (the sum of the two numbers is 21)&lt;br&gt;
(2) 5x+2y = 66  (5 times the first number plus 2 times the second is 66)&lt;br&gt;
Multiply (1) by 2:
(3) 2x+2y = 42&lt;br&gt;
Find the difference between (2) and (3) to eliminate y: 3x=24&lt;br&gt;
Solve: x = 8&lt;br&gt;
Substitute x = 8 into (1) to find y:
8+y = 21
y = 13&lt;br&gt;
Note that this solution is exactly equivalent to the good &quot;mental&quot; solution provided by another of the tutors.&lt;br&gt;
ANSWERS: 8 and 13&lt;br&gt;
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