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how do i figure out the answer to -2+4/5x=6

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4 Answers

If the equation is -2+(4/5)x=6, then

-2+(4/5)x=6

+2             +2

     

(4/5)x=8

 *5      *5

       

4x    =40

/4       /4

         

x    =10

 

If the equation is -2+4/(5x)=6

-2+4/(5x)=6

+2           +2

 

4/(5x)=8

*5x      *5x

 

4 = 40x

/40  /40

 

1/10 = x

Yes, you do need to isolate the 'x' on one side of the equal sign to solve the problem.

Hi Andrew,

By answer I am assuming you mean finding the unknown value (x). There are 3 things that you need to keep in mind when doing algebra:

 

1) You can only find an unknown value if you know every other value in the equation. So if you have more than one letter in there and they haven't given you the values for all but one of them, you lack the information to solve it.

 

2) Your goal is always to isolate the unknown variable on one side of the equal sign. So you always want it so the letter is by itself. You can do this by "undoing" the math. What I mean by that is you must figure out what cancels it or removes the operator by performing the opposite operation.

For example:

Given x - 2 = 0, isolate the x variable.

x - 2 = 0

  + 2

x      = 0

In the example I used addition, the opposite operation of subtraction to remove the -2 and leave the x by itself but the equation is still not right. This leads into the 3rd and most important thing to remember:

 

3) The MOST important thing to remember is that you have to do the same thing to BOTH sides of the equation. Think of the equals sign as a scale, if you have 2 pounds of candy on both sides of the scale the sides are balanced. Subtract one pound from a side and the scale is no longer balanced. It's your job to make sure the scale is always balanced. To go back to my first example:

In x - 2 = 0, solve for x. 

x - 2  =      0

  + 2      +  2

x       =      2

Therefore x = 2.

 

You can check your answer by replacing the x with your answer in the original equation. If you are correct, both sides should equal each other.

So then:

x - 2 = 0

2 - 2 = 0

     0 = 0   <------ They equal each other so the problem is correct.

 

If it is multiplication you must divide to cancel it.  3x / 3 = x

If it is division you must multiply to cancel it. x / 3 * 3 = x

If it is addition you must subtract to cancel it. x + 3 - 3 = x

If it is subtraction you must add to cancel it. x - 3 + 3 = x

As for your problem start off by getting rid of the -2 using cancellation on both sides.

Once you have the 4/5x isolated you have several options:

You can divide 4/5 by 4/5 remembering the copy, change, flip method.

(4/5) / (4/5) = 4/5 * 5/4 = 20/20 = 1

Or if you feel more comfortable you can break it apart remembering that (4/5)x = (4/5) * (x/1) = 4x / 5.

Undo the division first by multiplying both sides by 5.

Then undo the multiplication by dividing both sides by 4.

 

I hope this helps.

 

- Nick

 

The goal is to get x on one side of the = sign all by itself. To do that you gradually eliminate everything else that is on the side with the x. In this equation you could first add 2 to both sides of the equation to get 4/5x=8. Then you could multiply both sides of the equation by 5x to get 4 = 8 x 5x. Can you figure out the next step?