SOLUTION: I'm getting confused in the first step of equations with variables on both sides. For example: 7c- 4=9c- 11 I know that you put the variables together but I don't know when to add

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Question 15994: I'm getting confused in the first step of equations with variables on both sides. For example: 7c- 4=9c- 11 I know that you put the variables together but I don't know when to add , subtract, multiply or divide. Then if I do get help on it and get to the next step I'm getting confuse so please help me understand how to do these. Thanks,Kristen
Answer by elima(1433) (Show Source):
You can put this solution on YOUR website!
7c- 4=9c- 11
You are not alone with this. Many of my students are very confused when it comes to the negatives and positives.
In this example you would subtract 9c from both sides because it is a positive 9.
Lets say the problem was:
7c-4=11-9c
Then you would add 9c to both sides because it is a negative 9c.
Lets get back to the original problem;
7c-4=9c-11
First subtract both sides by 9c;
7c-4-9c=9c-11-9c
when doing that it cancels out the 9c on the right side and puts it on the left with the 7c.
Now you have 7c-4-9c=11
You can add sibtract the 7c and 9c since they are like terms;
-2c-4=11
Now we are going to add 4 to both sides since it is a -4 in the original problem;
-2c-4+4=-11+4
That cancels out the 4 on the right side and puts it with the 11;
Now the equation is;
-2c=-11+4
We add -11+4;
-2c=-7
Now we will divide both sides by -2 since it is being multiplied by the c;
=
c=3.5
I hope this helps some!
=)