PLEASE ANSWER AND EXPLAIN ILL MARK BRAINLIEST!!!!!!!!

Answer:
the answer of a is basically 13 plus 8, then 13 plus the answer to that, basically the number is adding the number right before it, 1+1=2 2+1=3 3+2=5 5+3= 8 8+5=13, so on and so on
Step-by-step explanation: