super mario brothers level 7 4

How do you get to world 4 and 7 on Super mario brothers (nintendo ds)?
on the ds, it goes from world 2, then down the bottom with a line attached, it has world 4 then another line goes up to world 5 but i can get to it by playing all the levels, it is the same with world 7.
how can i unlock these worlds to play ?
i have unlocked and finished all the other levels.
Try this
http://www.youtube.com/watch?v=Mg2tTKuzc98
New Super Mario Bros. Wii Walkthrough – World 7-4
super mario brothers level 7 4 AMAZON PRODUCTS BELOW
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New Super Mario Bros. (Nintendo DS) £18.95 The first all-new 2D Mario platformer since Super Mario World has arrived! Boasting incredible 3D graphics to accompany classic 2D gameplay, this fast-paced adventure will have Mario fans cheering as they make their way over fields, under water, through castles, and into the air. The power of the DS is used to great effect, and the result is that the Mushroom Kingdom looks more alive than ever. Ba… |