The purple highlighted square is missing the number 5. The red highlighted 5 eliminates
all but one of the empty tiles in this square. The remaining empty tile must be a 5.
Step 11
Simple Elimination
The purple highlighted column is missing the number 9. All but one of the empty tiles
are eliminated by the red highlighted 9's. The remaining tile must be a 9.
Step 12
Simple Elimination
There are four empty tiles in the purple highlighted column. One of them has to be a 6.
Three of them are eliminated by the highlighted 6's. The remaining tile must be a 6.