Answers according to the given drawing.
11) ∡1 + ∡2 = 180° => 12) ∡1 and ∡2 are supplementary angles
13) ∡3 + ∡4 = 180° => 14) ∡3 and ∡4 are supplementary angles
15) if it is ∡1≅∡3 then it is ∡2≅∡4
Good luck!!!
