The rules are simple, just adjust the equation to equal the result then confirm it by pressing the Equal or Different sign.

(the demo only has exercises ending in 24. Purchase the Full game to access the entire repertoire of exercises)

Notes:

• The (Online and Android) Demo only has exercises targeting 24 and only saves the Volume
• Difficulty = 0 is True/False in which you have to choose if the equation is equal to the target or not. You won't gain Stars in this mode.
• There is a Tutorial which explains the concept with detailed examples (press "How to Play?" in the menu)
• Stars are lost when skipping