Answer:
A. 21
Step-by-step explanation:
So okay I did this just the other day, I'll explain how I got this answer. First Vertical angles are congruent, so 64 is the known value and (3x+1) is the unknown value, but they are both congruent because they are Vertical angles. So this is what I did, I tried to figure out what was x because something times 3 plus 1 would give you 64. So I subtracted 1 from 64 (the one from 3x+1) and divided 63 (the value after subtracting 64-1=63) and got 21 so X= 21