Question 65176
{{{D=(C-S)/N}}}

We want to get the S variable isolated (alone-ified) on one side of the equation.  First, we move the N.  To move the N, multiply both sides by it.  We do this because (C-S) is all divided by N, and the only way to subtract C so we can get S is to first multiply by their dividend, N.<br>

{{{D=(C-S)/N}}} so times N to both sides:
{{{D*N=(C-S)/N*N}}}=>{{{DN=C-S}}}<br>

See that, we've almost got S by itself!  Now to get rid of that pesky little 'C.'  Simply subtract both sides by C!<br>

{{{DN-C=C-S-C}}}=>{{{DN-C=-S}}}<br>

We're <s>done!</s> almost finished: We have to rid ourself of the 'negative' sign!  We know that -S is the same as saying -1 times S [-1*S], so we multiply both sides by -1, since -1*-1=1:<br>

{{{(DN-C)*-1=-S*-1}}}=>{{{-(DN-C)=S}}}  S is isolated!  We're <s>FINALLY DONE!!!</s> almost there..  We just have to distribute the '-' on the left:<br>

{{{(-1)DN-(-1)C=S}}}=>{{{-DN-(-C)=S}}}  Recall that -(-x)= a positive x, so 
{{{-DN+C=S}}}  We can optionally arrange this to our liking,
{{{C-DN=S}}}.  There, it's a simple as that!  Ask any questions you need to.