Prove xvz = wvy we are given an image of wz and xy, which intersect at point V. m xvz + m zvy = 180 by the definition of supplementary angles. m zvy + m wvy = 180 by the definition supplementary angles. Since the sum of m xvz + m zvy + m wvy by the transitive property of equality, m zvy can be subtractraced from both sides of the equation because of the subtraction property of equality. therefore m xvz=m wvy and xvz = wvy by the definition of congruent angles which theorem does it offer proof for?