Oh I remember doing this last year and boy was it tough, I really have absolutly no clue, my teaher was terrible at explaining things and she for some reason told the answer to the class on the test which really didn't help me as I had no clue how to show the work

EDIT: I think I just rembered it, If im not mistaken it had something to do with those if-then statments. Maybe something like " If angle is is congruent to c, And angle c is congruent to angle d. Then angle a must be congruent to angle D based on the givin facts" Hope this helps, all I can seem to remember for now.