Here's a question I've come across and I am stuck...

The questions goes like this (even though there are no six in the question which puzzles me)

Replace as many of the digits 5, 6, 7, 8 with a zero as are necessary to make this addition correct.

555

777

888

999+

___

1111

This is my attempt. I guess, 9 cannot be made zeros, (as question doesn't mention it) so I did this but it's not correct.

005

007

000

999+

___

1111

Any help would be very much appreciated... Thanks