the average age of a class of 12 students is 19 years . the average increased by 2 when the teacher ' s age also included . what is the age of the teacher ?
"if age of the teacher was 12 , average would not have changed . since average increased by 2 , age of the teacher = 12 + 22 × 1 = 34 answer : b"
subtract(multiply(add(12, 2), add(19, 2)), multiply(12, 19))