Please Help Me Solve Problems Like This... 12-1/5r=2r+1

Guest2017

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I understand that I need to get the variable on one side so I should subtract 2r from both sides. I do not understand that when I subtract 1/5r-2r I get -11/5r. What is the mathematical process I am completing? I also need help completing the additional steps to get to the answer which is 5r. Please help, thank you in advance.
 

Jomo

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-1/5 - 2 = -1/5 - 10/5 = -11/5
Just like 7r - 3r = (7-3)r = 4r

The answer would be in the form r = some number, so I doubt the answer is 5r.
Please show us your work.
 

tkhunny

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12-1/5r=2r+1

They are just numbers. Is the fraction confusing you? Your chosen pathway seems fine. Where do you think it went wrong?

12 - (1/5)r - 2r = 2r + 1 - 2r

12 - r((1/5) + 2) = 2r - 2r + 1

12 - r((1/5) + (10/5)) = (2r - 2r) + 1

12 - r(11/5) = (0) + 1

12 - (11/5)r = 1

Okay, now what?
 

Guest2017

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Thank you for the reply and sorry I guess I am not explaining my issue correctly. I don't know how to solve 1/5r-2r. I have the answer and the steps to find the correct answer but I don't understand some of the processes I am completing in this particular problem. So when this type of problem comes up again I don't know how to solve it.
 

Jomo

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Thank you for the reply and sorry I guess I am not explaining my issue correctly. I don't know how to solve 1/5r-2r. I have the answer and the steps to find the correct answer but I don't understand some of the processes I am completing in this particular problem. So when this type of problem comes up again I don't know how to solve it.
So please show us the steps you have and which part(s) you do not understand.

-1/5 - 2 = -1/5 - 10/5 = -11/5 so (-1/5)r - 2r = (-1/5 - 10/5)r = (-11/5)r. What do you not understand? I posted this above, if you did not understand it then say exactly what you do not understand. It really makes it easier to help you if we know where you are confused.
 

tkhunny

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Thank you for the reply and sorry I guess I am not explaining my issue correctly. I don't know how to solve 1/5r-2r. I have the answer and the steps to find the correct answer but I don't understand some of the processes I am completing in this particular problem. So when this type of problem comes up again I don't know how to solve it.
You don't have (1/5)r - 2r. You have -(1/5)r + 2r.
 

Guest2017

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Hello again,

12−1/5r=2r+1
I know I need to get r on one side so I would subtract 2r from both sides. How do I subtract 1/5 - 2r? It would help to know in words how to solve the equation. I'm on Khan Academy so I can get hints to find the answer but I don't know how to solve the equation above without help. Thank you hope this is more specific. After I understand how to do that step I will show you the next step I am having difficulty with.
 

Jomo

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You can NOT simplify 1/5 -2r as they are not like terms. If instead you mean (-1/5)r - 2r I showed this to you a few times now. Unless you explain why you do not understand what I am showing, it will be my last time helping you.

Easier example: -3r - 7r = (-3-7)r = -10r
(-1/5)r-2r = (-1/5 -2)r = (-1/5 - 10/5)r = (-11/5)r. If this is not clear to you, then please explain what you are not understanding.
 
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