Question 193899
Sum of the angles in a triangle is 180 degrees
{{{180 = R + S + T}}}
{{{180 - S - T = R }}}
{{{180 - (12x-15) - (3x+30) = R}}}
{{{180 - 12x + 15 - 3x - 30 = R}}}
{{{165 - 15x = R}}}