Level 19 (Light the Fuse)
65 balloons required to complete the level. Another fairly easy level to fully complete. All you need to do here is to hit one of the pins, the one on the left hand side is easiest, and all the other bloons will pop along with that pin bloon.
Level 27 (Bouncy)
15 balloons required to complete the level. Once again we are playing contrary to a previous level. This time for your first shot try to take out all the ice bloons which are under the horizontal brown wall. This freezes all the bloons above the brown wall. Next shot try to bounce off those frozen bloons with a low arc and your dart will hopefully end up among the bloons in the vertical part. Fingers crossed you clear enough to complete the level, a score of 40% is not unreasonable on this level, anything above is good and luck seems to be on your side.
Level 33 (Danger!)
30 balloons required to complete the level. If you think this level looks simple, look again, the ice bloons make it harder than you might think. With the first dart aim for the group on the right, make an arc over the top of the ice bloon hitting the pin bloon on the right. For the group on the top right try to take out the pin bloon which is on the right of the group. For the group which is on the top left do the same as the other one, trying to take out the pin bloon on the right. Hopefully you will end up with about 10 bloons from each block to make up your target score of 30.
Level 45 (Not so Hot)
20 balloons required to complete the level. As surprising as it may seem you can get to the target without balloons breaking any walls, however you do have to get all three dart bloons and the Pac-man one. The first shot is possibly the most important as you need to have the correct arc to get both the dart bloons directly in the line of fire and also the Pac-man one on the way down. Once you have the Pac-man you can eat your way directly through the brown wall and into the main group of regular bloons. Eat as many as possible before time runs out, and if you have positioned the Pac-Man correctly you should be just able to get all the way up the right hand two columns of the group and make a start coming down the other side of the main group, thereby getting enough to meet your target. If you have any darts left you can try to get extra bloons by breaking the wall.