Answer :

MengXiong1

Answer:

-9

Step-by-step explanation:

Step 1 : Put like terms together

x + 9 = 21 + 3x - 4 + 10

Subtract 3x on both sides

-2x + 9 = 21 - 4 + 10

Subtract 9 on both sides

-2x = 21 - 4 + 10 - 9

Simplify

-2x = 18

Step 2 : Divide

[tex]\frac{-2x}{-2}[/tex] = [tex]\frac{18}{-2}[/tex]

x = -9

Answer:

x= -9

Step-by-step explanation:

- Put all the same signs together

x-3x = 21-4+10-9

*Quick tip:

  -when you cross a sign with a number or without a number over the equal  

   sign you have to change the sign (positive to negative and negative to    

   positive.

  -x and 1x is the same thing

- Calculate small sections by small sections

-2x = 17 + 1

-2x= 18

-2/-2x = 18/-2

x= -9

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