Question 1171400
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As tutor @ikleyn says, the easiest way to solve this problem is using a single variable.<br>
The path she used to the solution is a good one; here is an alternative.<br>
Learn from this that there are nearly always different ways to set up a problem for solving.<br>
As you are learning mathematics, always explore different ways of solving problems and find ways that "work" for you.<br>
Start the same way she does: the first number is x, so the second is 2x.<br>
Now go a different direction than she did. "the sum of the first two numbers is 2 more than the third number" --> "the third number is 2 less than the sum of the first two": the third number is 3x-2.<br>
Now the equation to be solved says that the sum of the three numbers is 40:<br>
{{{x+2x+(3x-2)=40}}}
{{{6x-2 = 40}}}
{{{6x = 42}}}
{{{x = 7}}}<br>
ANSWERS:  The three numbers are
x = 7
2x = 14
3x-2 = 19<br>