what number should replace the question mark ? 3 , 30 , 11 , 24 , 19 , 18 , - - - ?
"answer : c 3 , 30 , 11 , 24 , 19 , 18 , 27 ? there are two alternate sequences : + 8 and - 6 ."
add(add(add(3, 3), 3), 3)