180° because it is half of a full circle(360°)
To work out what the other side is that you times 12 to get to 24 you would do: 24 divided by 12 equals 2 therefore you would do 12 times 2 to get 24
Hope this helps. Let me know if you have more questions.
There are a lot of vertical angles in this figure, I will try my best to list most of them; ace,bcg bca, ecg gfd,afe gfe, dfa
