Just some tips i pulled from the guide I made on x360a:
42 isn't very bad, and many people may get this without even having to replay. If after completing the 100 levels go back and replay beginning levels and put to use your skill increase. Surprisingly levels 80-90 were quite easy for me to 3 star if you're really srounging for some, and steer clear of 90-100.
-Learn to combo your combos This is the best tip I have, combining 3 line clears is nice, clearing 2 lines thick in 3 directions, especially for levels that have hexes in areas that cannot be gotten through normal combining. Even better however is combining a color clear with two line clears, it turns every hex of that color to a line clear, and immediately fires them. Learning to do this well is really all you need to finish this game.
-Most levels are not timed, no need to act like they are, go ahead and think about more than the current move to make a juicy combo.
-The anomaly drop levels drop the anomalies on specific turns, but its still important to get the earlier anomalies down fast, if you get two or more near the bottom it gets really hard
-On anomaly levels with multiple obvious paths, try to clear one path and, if possible, exclusively clear hexes on that path so the anomalies drop onto it
-On dark frag levels clear bottom first, specifically bottom corners, the top may largely clear itself
-When on tricky dark frag levels make note of where you were having trouble clearing and clear it first
-Timed levels are usually pretty easy to beat, but hard to 3 star, at least for me, so I tried to steer clear of them for The Number
-These are the levels I did for The Number I don't consider myself very good at this game, so while some luck may have been involved for some most of these should be doable; 1-7, 11-17, 19, 20, 23, 27, 28, 36, 38, 41, 44, 50-52, 60, 61, 65, 69, 70, 81-85, 87, 89, 100