To sum up all the comments and add some details on the diffrent subgames. Unlock the games by playing daily brain challenge. I had them all unlocked when I reach 100% but I reached 97% before I started "cheating". so I had them all unlocked.
Tools recommended: Paper and pencil and a digital camera or mobile phone with camera.
Balance: Select the heaviest item ignore what they look like, but make sure you notice the scale isn't boolean, ie the height will help solve some of the combinations. Taking photos makes this game a breach but just pausing while thinking will be enough to beat it.
Magic Rule: Look at the three rules, to find the solution of the fourth. Photos makes this easy but pausing and thinking will take you through it.
Impression: Count the impressions and focus on weird shapes position and you can do this by pausing and thinking. Photos will as usual make it very easy.
Combinations: You can basically ignore the "signs" and only focus on the changes. Pausing and focusing on atleast two corners will solve almost all combos in a single pause. photos remove all challenge.
MATH: You shouldn't need a calculator use one if you want
Troute Route: Pause calculate,unpause move, remember to move directly if their is only one possible path. and you will solve it without the need of photos.Photos will improve your score.
Arithmetic: Be carefull when you pause or you will be unable to move. pause, calculate,unpause feed in the answear, quick look, pause... No use of photos.
Tick Tock: Look on first watch , pause, note it down, unpause look att second watch, pause Note it down, calculate diffrence,unpause feed the answear in. You can use photos instead of a note pad, this will give you time to watch the options and you might not need to calculate and instead rule out the wrong answears.
Match Stick: Photos is the best option here, but you can solve them with a notepad and the pause button aswell. Easy doesn't require either.
Traveling: Just follow the path, this is the easiest game of them all. If you just remember that the path never cross itself you can figure out how the path went on the fast one even if it's just flashing quickly on the screen.
Hocus Pocus: Focus on the colours and order, not the shapes. and you will solve them by pause and notes. photos will makes it easy.
Order:, Pause and note down the color and shape on paper then just feed in the answear. Photos are not a good option here.
Garage: Look, pause,calculate,unpause, look, pause, sum on the Hard difficulty. easy and medium can be done without pausing.
I solve this one on easy without pausing, but i recommend Photos on all difficulties. It's just hard to see the diffrence between 9,10,11,13 blocks of diffrent colors if they are nested. You can do this with pausing and thinking aswell.
Mosaic: One of the easy once that doesn't require any cheating. just feed in the shapes and don't be bothered about the "slow" you get on the big ones. Photos will improve your results.
Reflection: Photos are the best option here, you can probably handle Easy without it.
Face: Is a child game on easy and quite easy on Medium if you remember to look at the characters cheek shape. But photos really help on Hard so you can find the minor diffrences between the characters without stress.
Select the fastest moving and highest jumping ball. This one is hardest of the games if you use "cheats" because you can't cheat in it. But if you wouldn't cheat this one is quite easy in comparison with many others.
Numbers: Easy and medium is not hard without cheating. Hard is easy with a photo so you can look at the options in peace and not the diffrences. you can then unpause and look for the "diffrence" or you can pause/unpause while noting down the numbers on a paper.
Ninja: My favorite Game. You solve them easily on all difficulties by just looking and pick the right answear. however if your brain can't keep up with the flashing ninjas, make sure your not tired and practise.
Frog: Photos makes this one easy. Pausing and thinking will do, if you can solve Easy with one pause per pattern. Medium and Hard is solvable with several pause/unpause.