Need to undo tile using keyboard shortcuts only

Taking a class on excel now and doing everything with keyboard shortcuts only.

Need help with the tile functions...

To tile is fine, alt+window and select tile, but how can I undo without using the mouse...I can alt+spacebar but resizing for the window comes up. I need it restore book to normal size in the open excel window. Not just the window.

Anyone know of keyboard shortcuts I can use?