3 years ago the average age of a class of 6 members was 19 years . a boy have been added , the average age of the class is the same today . what is the age of the boy ?
6 * 22 = 132 7 * 19 = 133 ` 1 a
subtract(multiply(add(6, const_1), 19), add(multiply(6, 19), multiply(6, 3)))