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3x-4(2x+5)=-16 +13x

Seems easy, but...I want to be sure I am using the correct order
Thanks
 
C
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4 Answers

Follow order of operations. WAIT, can't combine 2x+5, BUT we can DISTRIBUTE something. So distribute to EVERYTHING in the ( ) then combine like terms to get -5x-20=-16+13x   Now get anything with an x on ONE side. Then get x all by itself. Finally x=(-2/9)
3x-4(2x+5)=-16 +13x
1.remove parentheses  3x-8x-20=-16+13x
-5x-20=-16+13x  2. add 5x to both sides get -20=-16+18x
3. add 16 to both sides get -4=18x
4. divide by 18 get -4/18=-2/9=x
Multiplication comes before subtraction, so first you must distribute 4(2x+5). Also you must remember to subtract both terms from 3x. After this step you end up with 3x-8x-20=-16+13x. Next you put all x terms together and all constants together. If you put all constants on the left and x terms on the right, you end up with -4=18x. Dividing both sides by 18, you get x=-4/18=-2/9.
3x-4(2x+5)=-16+13x
 
You have to first multiply 2x+5 by -4 before you can begin combining the other terms.
-4*(2x+5)=-8x-20 so...
 
3x-8x-20=-5x-20=-16+13x
 
then add 16 to both sides and add 5x to both sides
-5x+5x-20+16=-16+16+13x+5x
-20+16=13x+5x
-4=18x
 
divide both sides by 18
-4/18=18x/18=x
-2/9=x