Question 596193
{{{D= (8C-s)/(4n)}}}


{{{D*4n= 8C-s}}}


{{{4Dn= 8C-s}}}


{{{4Dn+s= 8C}}}


{{{s= 8C-4Dn}}}


So the solution is {{{s= 8C-4Dn}}}