1=45
2=135
3=135
6=45
7=45
8=135
9=90
12=90
4 and 1 are opposite, and thus equal, angles.
7 and 5 are supplementary angles, and thus they add up to 180 degrees. To get 7, you subtract 135 degrees from 180.
9 and 10 are supplementary and equal since all four those angles are 90 degrees.
