Check the picture below. If the angles are supplementary the a || b.
[tex]\bf (x+85)+4(x-20)=180\implies (x+85)+(4x-80)=180 \\\\\\ 5x+5=180\implies 5x=175\implies x = \cfrac{175}{5}\implies x = 35 \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\measuredangle (x+85)}{(35)+85\implies 120}\qquad \qquad \stackrel{\measuredangle 4(x-20)}{4(35-20)\implies 60}[/tex]
