Question 990743
x, the unknown angle measure;
180-x, the supplement of x;
{{{x=-20+3(180-x)}}}, the description transcribed into an equation.


SOLUTION STEPS
{{{x=3*180-3x-20}}}
{{{x+3x=3*180-20}}}
{{{4x=3*180-20}}}
{{{x=3*45-5}}}
{{{highlight(x=130)}}}


Steps can vary as long as correct operations on both sides are followed.