Question 948251
{{{S=7+C}}}
{{{S*C=78}}}
Substituting,
{{{(7+C)C=78}}}
{{{C^2+7C-78=0}}}
{{{(C-6)(C+13)=0}}}
Only the positive solution makes sense here.
{{{C-6=0}}}
{{{C=6}}}
So then,
{{{S=7+6}}}
{{{S=13}}}