Question 982507
1.{{{A=5C}}}
2.{{{A+C=90}}}
3.{{{A+S=180}}}
Subtracting eq. 2 from eq. 3,
{{{A+S-A-C=180-90}}}
{{{S-C=90}}}
{{{S=90+C}}}
Substituting eq. 1 into eq. 2,
{{{5C+C=90}}}
{{{6C=90}}}
{{{C=15}}}
So then,
{{{S=90+15}}}
{{{S=105}}}