the average of 1 st 3 of 4 numbers is 6 and of the last 3 are 3 . if the sum of the first and the last number is 13 . what is the last numbers ?
a + b + c = 18 b + c + d = 9 a + d = 13 a – d = 9 a + d = 13 2 d = 4 d = 2 answer : b
subtract(subtract(multiply(3, 6), add(subtract(13, 6), 3)), 6)