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2x + 5 = 47variable equations

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aranna3028 | Student, Grade 9 | (Level 2) eNoter

Posted March 12, 2009 at 10:41 AM via web

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2x + 5 = 47

variable equations

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cburr | Middle School Teacher | (Level 2) Associate Educator

Posted March 12, 2009 at 10:58 AM (Answer #1)

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The key to answering this kind of question is that you want to do whatever is necessary to get the unknown -- the letter -- by itself on one side of the equals sign.

2x + 5 = 47

First you want to get rid of the 5.  Subtract 5 from both sides of the equation:

2x + 5 - 5 = 47 - 5

2x             = 42

Now you need to get rid of the 2.  You can divide both sides by 2:

2x/2 = 42/2

x     =  21

 

Top Answer

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bridgetrbcs | High School Teacher | (Level 2) Adjunct Educator

Posted March 12, 2009 at 11:00 AM (Answer #2)

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Hi!!  I always tell my students to pretend that we are playing a game of undo what the teacher has done in order to solve equations.

For example, in the first one you are multiplying the 2 and x and adding the 5.  To undo those operations you do the opposites.  Multiplying and dividing undo each other while adding and subtracting undo each other.  So to undo this problem we will subtract the 5 and divide the 2.  Here's how to do it step by step.

2x +5 = 47 (We always undo the number with no letter FIRST!)

2x +5 -5 = 47 -5 (Subtract the 5 to undo the adding.)

2x = 42 (-5 +5 equals 0)

Now divide by 2 to undo multiplication.

2x/2 = 42/2

x = 21

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nayem | Student, Grade 10 | eNotes Newbie

Posted March 20, 2009 at 5:42 PM (Answer #3)

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x=21                         

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princessita-2-day | Student, Grade 12 | (Level 1) Valedictorian

Posted January 2, 2012 at 10:01 AM (Answer #4)

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2X+5=47 here are the rules to solving

Rule 1: look at the question

Rule 2: how many terms [in this case it is three]

Rule 3:Do the opposite operation of the number by 2X [the term you are solving for]. transfer the number to over the = sign

Rule 4: After the opposite operation divide the answer you got using the opposite operation with the variable you are solving for. so it is like this: 2X+5=47

opposite operation: 2x=47-5

2X=42

in order to let the x by itself divide the number by it

so 42 divided by 2 is 21.

 

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atyourservice | Student, Grade 10 | (Level 3) Valedictorian

Posted April 14, 2014 at 9:42 PM (Answer #5)

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2x + 5 = 47

combine the like terms by minusing 5 on each side.

2x + 5 = 47

     - 5   - 5

2x = 42

now divide by 2 to get x by itself

`(2x)/2 = 42/2 `

x= 21

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Wiggin42 | Student, Grade 11 | (Level 2) Valedictorian

Posted May 24, 2014 at 7:54 PM (Answer #6)

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We want to solve for x given: 

2x + 5 = 47

First, we undo any addition or subtraction: Since five is being added, we will subtract. 

2x = 42

Then we undo any multiplication or division: Since two is being multiplied, we will divide. 

x = 21

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jess1999 | TA , Grade 9 | (Level 1) Valedictorian

Posted June 19, 2014 at 5:19 AM (Answer #7)

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2x + 5 = 47

To solve this equation first subtract 5 from both sides

By subtracting 5 from both sides your equation should look like

2x = 42 now divide both sides from 2

By dividing both sides from 2 your equation should look like

x = 21 which is your answer

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ik9744 | TA , Grade 9 | (Level 1) Valedictorian

Posted June 20, 2014 at 2:41 AM (Answer #8)

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Equation:

2x+5=47

2x+[5-5]=47-5

2x=42

2x/2=42/2

x=21

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zumba96 | TA , Grade 11 | (Level 2) Valedictorian

Posted June 22, 2014 at 7:14 PM (Answer #9)

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Isolate the variable first

2x + 5 = 47

Now move 5 to the other side

2x=47-5

2x=42

Now divide x by 2 to get x

x=21

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malkaam | TA , Undergraduate | (Level 1) Valedictorian

Posted October 14, 2014 at 8:40 PM (Answer #10)

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2x + 5 = 47 

The key finding this is to isolate x, which is unknown,

2x+5-5=47-5  (subtracting 5 on both sides)

2x=42

2x/2=42/2       (dividing both sides by 2)

x=21 Answer.

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