consider a string consisting of a's, b's, and c's, where the number of b's is three times the number of a's and the number of c's is five times the number of a's. prove that the length of the string is divisible by 3. proof: suppose s is a string of length n that consists of a's, b's, and c's, where the number of b's is times the number of a's, and the number of c's is times the number of a's. let x, y and z be the numbers of a's, b's, and c's in s, respectively. the length of s is the ---select--- of the numbers of a's, b's and c's that are in s. hence, n
