The MetaShkola website (Russian language) provides past problems and solutions.
A three-digit number is divisible by 9. If you swap the first and last digits, the new number is also divisible by 9. How many such numbers exist where the middle digit is 5? Part 3: Geometry & Spatial Thinking (15 points each) metashkola olimpiada po matematike zadaniia
Platforms like YouTube offer walkthroughs for similar Russian-style olympiad problems. metashkola olimpiada po matematike zadaniia