Ask for your money back on all those chemistry classes, Tom and Ray. Although I suspect if someone plunked down a $10 bill you’d remember the right answer in a hurry.
Aluminum valence usually= 3 AL+++
Carbonate (CO3) valence =2 (CO3)–
Ergo Aluminum Carbonate needs 2 Aluminums for every 3 carbonates to share 6 electrons right
The Chemical industry and everyone in West Virginia thanks you for repairing their cars all these years and not being chemists!