Alfredos house number is between 20 and 35. The sum of the digits is less than 5. If you subtract 1 from it you would get a multiple of 3. If you add three, you get a multiple of 5. What is Alfredos house number.

This question is for my nine year old niece. Any help would be appreciated.

Thanks aunt Patty

The place to start is with the second clue, "If you subtract 1 from it you would get a multiple of 3." The multiples of 3 between 20 and 35 are 21, 24, 27, 30 and 33. Thus Alfredos number is

Now use the first clue and then the third clue to eliminate some of these possibilities.