m∠3 is = 57º for this is an alternate interior angle
1) As we have a pair of parallel sides intercepted by a transversal line, then it's safe to say that
∠ 1 is an alternate interior angle and therefore m∠1 = 33º
2) The other leg of that triangle is another transversal line, so we can state that
m∠3 is = 57º for this is an alternate interior angle