AnkiApp lets you organize related decks by using tags, and study them together. When you add a tag to a deck, it then appears under the Tags section of the My Decks screen.
To tag a deck, from the Deck screen, open the menu, then select "Edit Deck".
Then use the New button in the "Tags" section to add new tags.
On the My Decks screen, the tag "math" now appears under the "Groups" section.
When you select the "math" tag, you're taken to the "Deck Group" screen, which lists all decks with that "math" tag.
From here, you can review all decks with the tag, or select individual decks to visit the Deck screen for one of the decks you see.