You will need to unlock every minigame through play mode before you can get this achievement. There are a total of 27 minigames (7 each for Language, Numeracy and Logic, and 3 each for Visual and Memory) and you can view which ones you have unlocked by going into 'Coach'. In coach mode, select an available minigame and play through bronze and silver to get to gold. You will need to answer every question correctly to earn the medal. Gold is the toughest of all 3 medals to get because the minigames will be harder and you will have less time to answer. If you get the answer to a question wrong, you can hit and select ‘Restart Game’ or for some minigames you might want to play to the end to try and learn some of the answers. Don’t be discouraged if you don’t get the answers right immediately, as this will take a lot of practise for many of the minigames.
For help with strategies, check out -This- thread.