The answer is 105. Alternate interior angles of two parallel lines are congruent(meaning they are the same). 210/2=105, also the answer has to be below 180 degrees but more than 0.
I know this because if you add 4 to 43 that's 47 so that's 1 of the blanks. Add another 4 that's 51. that's another 1. and that's last one is add 4 which makes 54.
