a certain experimental mathematics program was tried out in 2 classes in each of 42 elementary schools and involved 55 teachers . each of the classes had 1 teacher and each of the teachers taught at least 1 , but not more than 3 , of the classes . if the number of teachers who taught 3 classes is n , then the least and greatest possible values of n , respectively , are
"one may notice that greatest possible values differ in each answer choice in contrast to the least values , which repeat . to find out the greatest value you should count the total classes ( 42 * 2 = 84 ) , then subtract the total # of teachers since we know from the question that each teacher taught at least one class ( 84 - 55 = 29 ) . thus we get a number of the available extra - classes for teachers , and all that we need is just to count how many teachers could take 2 more classes , which is 29 / 2 = 14.5 . so the greatest possible value of the # of teachers who had 3 classes is 14 . only answer b has this option ."
divide(subtract(multiply(42, 2), 55), 2)