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Given that 2x-5=3(2x-2)-15, WHAT IS THE EVALUATION OF 2X+1?

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3 Answers

Let u = 2x+1. Then 2x-5 = 2x+1-6 = u-6, and 2x-2 = 2x+1-3 = u-3.
So,
 2x-5=3(2x-2)-15 becomes,
u-6 = 3(u-3)-15=> u-6 = 3u-24
=> 18 = 2u
=> u = 9
Answer: 2x+1 = 9
One thing which might be confusing in this problem is the wording. "What is the evaluation of 2x+1" is just funky math-speak for "what number is 2x+1 once you plug in x." To do this, we can solve the equation they give us, and then we'll plug in x.
 
 
Let me show you a similar example: Given that  3x - 2 = 4(2x - 2) - 14, what is the evaluation of 3x + 2?
 
We'll start by solving for x:
3x - 2  =  4(2x - 2) - 14
3x - 2  =   8x - 8    - 14
3x - 2  =  8x - 22
      +22        +22
 
3x + 20  =  8x
-3x             -3x
 
20  =  5x
/5       /5
 
4    =  x
 
Now we know that x is 4. Therefore, 3x+2 evaluates to  3(4) + 2,  which is better known to its friends as 14.
 
 
Take home message: The phrase "evaluation" means "what number do you get when you plug in for all of the variables." Hopefully this is enough to help you make some progress. :-)