okay so from my understanding, this is either geometry or trig. i took both classes last year, and I don't quite remember everything so I'll answer these questions to the best of my understanding.
1= exterior sides in opposite rays
2= given
3= supplementary angles
4= subtraction property
5= second substitution
6= first substitution
7= if corresponding lines are equal, then lines are parallel.
hope this helps you brother, have a good day dude!