7n-3=4n+12

Question

i dont understand if you have to plus or minus

Answer 1

To COMBINE 'LIKE' terms, you need to get all of the "n stuff" onto one side of the equation, and all of the "constants only" stuff onto the other side.

 

In this case, subtract 4n from each side. This has the effect of MOVING 4n TO THE OPPOSITE SIDE OF THE EQUATION, WHERE IT TAKES ON THE OPPOSITE SIGN" 7n - 4n -3 = 12

 

3n = 12 + 3, next! 3n = 15; n = 5.

 

THIS PROCESS IS CALLED TRANSPOSING TERMS and it is a perfectly safe technique, JUSTIFIED BY THE IDEA OF adding opposites to each side of an equation.  THIS PROCESS MAKES STUDENTS PROFICIENT IN ALGEBRA.

It is a GREAT PITY that this idea of efficiency is not taught.

Answer 2

What we are trying to do is isolate the variable (x) so we will need to do a few things to our equation.

 

7n-3=4n+12

 

First let's add 3 to both sides so that we will have 7n = 4n + 15

Next, we'll subtract 4n from both sides to end with 3n = 15

Last, we need to divide both sides by 3 so we can find the value of n.

 

Our final answer is n=5