Which expressions represent the difference of exactly two expressions? Choose 3 answers:
6(x + 7) - 2
-21
4f - 2g
3.xyz - 10

M∠abc=138° and m∠def=31° . which statement is true about ∠abc and ∠def ? a: the angles are neither complementary nor supplementary. b: the angles are complementary. c: the angles are supplementary.