1. We will call a non-negative integer a zebra if even and odd digits strictly alternate in its representation. Can the difference of two 100-digit zebras be a 100-digit zebra?
Answer: Yes. Solution. Here is one of many possible examples: $5050 \ldots 50-2525 \ldots 25=2525 \ldots 25$

Grading Guidelines. An obviously correct example, or a correct example with justification of its correctness - 7 points. A correct example, for which additional calculations are required for justification, not performed by the author - 5-6 points, depending on the difficulty of the remaining part of the justification. The idea of constructing an example without a specific example - 1 point.