The purple highlighted column is only missing 1, 3, 6 and 9. The red highlighted numbers
eliminate 1,3, and 6 from the tile with the red x. The only remaining number for that tile is 9.
Step 23
Simple Elimination
The purple highlighted square is missing the number 2. The red highlighted 2 eliminates
alll but one of its empty tiles. The remaining empty tile must be a 2.
Step 24
Simple Elimination
The highlighted row is missing the number 2 and has two empty tiles. The red highlighted two eliminates
one of the tiles, the other one must be a 2.