what number should replace the question mark ? 5 , 24 , 11 , 20 , 17 , 16 , - - - ?
"answer : b 5 , 24 , 11 , 20 , 17 , 16 , 23 ? there are two alternate sequences : + 6 and - 4 ."
add(add(add(5, 5), 5), 5)