"ab" = 10a + b
So we want x, y such that
which is ridiculous.
So try 3 digits, abc:
This, at least, might be possible. We need 29a - b to be divisible by 4 with a and b in the range from 0 - 9. By trial and error I immediately run into (a, b) = (1, 1):
So 711 fits the bill.
See if you can find others.
What can you say about a 4 digit number?
Solve this for d and see if you can find any a, b, c for it and why/why not.