# Thread: Solving for a varible

1. ## Solving for a varible

I have an equation filled with variables, needing to solve for just one of them..

S = n*a + (n - 1)*d , solve for n

* = multiplication

what on earth do I do for this?

2. You can use the distributive property on $(n-1)d$ which is $nd-d$

Once you've done that collect any terms with n in on one side and those without on the other side - this means you'll be able to factor out the common factor n

3. Ok I think I may have figured it out... Just to be clear:

1) distribute the d through (n-1) to make your equation

S = na + dn - d

2) pull out the n from na and dn to make

S = n(a + d) - d

3) now divide both sides by a + d to get

S/a+d = n - d

4) then add d to both sides to get the final answer of...

n = S + d/a + d

right?

4. Originally Posted by gurrry
Ok I think I may have figured it out... Just to be clear:

1) distribute the d through (n-1) to make your equation

S = na + dn - d

2) pull out the n from na and dn to make

S = n(a + d) - d
Add 'd' to both sides here..