Question

How many positive integers less than 1000 have the property that the sum of the digits of each such number is divisible by 7 and the number itself is divisible by 3 ?

Answer 1

Sum of the digits is divisible by 7 and number itself is divisible by 3

∴ x + y + z = 21, x, y, z are digits 0, 1, 2, ...., 9.