Any number that is divisible by 3 is also divisible by 9.
find a counterexample to show that the conjecture is false.
18
27
45
48

For a number to be divisible by 9 the sum of the digits is also divisible by 9.
For the examples given 48 (4+8 = 12) (1 + 2 = 3) therefore 48 is not divisible by 9 as the sum of the digits is 3.

For a number to e divisible by 3 the sum of the digits is also divisible by 3. (eg 48 (4+8 = 12), (1 + 2 = 3) therefore 48 is divisible by 3