Question 1018350
{{{A=18+S/2}}}
{{{A+S=180}}}
Substituting,
{{{18+S/2+S=180}}}
{{{(3/2)S=162}}}
{{{S=(2/3)162}}}
{{{S=108}}}
Then,
{{{A=18+108/2}}}
{{{A=18+54}}}
{{{A=72}}}