Question 1046708
Two angles are supplementary. 


{{{x+y=180}}}




One angle measures 15 degrees less than the other one.


{{{x=y-15}}}




Try the obvious substitution.  Just be careful as you make the substitution.  
{{{x+y=180}}}
{{{(y-15)+y=180}}}
{{{y-15+y=180}}}
{{{2y-15=180}}}
{{{2y=180+15}}}
{{{2y=195}}}
{{{y=195/2}}}
{{{highlight(y=97&1/2)}}}
and the other angle is {{{97&1/2-15=highlight(x=(82&1/2)degrees)}}}.