Question 1055427
{{{(1/3)S=C-15}}}
and
{{{A+S=180}}}
{{{A+C=90}}}
So,
{{{S-C=180-90}}}
{{{S-C=90}}}
Substituting,
{{{3(C-15)-C=90}}}
{{{3C-45-C=90}}}
{{{2C=135}}}
{{{C=135/2}}}
So then,
{{{A+135/2=180/2}}}
{{{A=45/2}}}
and
{{{S-135/2=180/2}}}
{{{S=315/2}}}