For 19 you can get a line of symmetry between each one that is hand to hand (wing to wing) and each one that is nose to nose. Those total 7. In other words, you can make a fold in many places if you take two at a time (or individuals which is what the problem asks).
For 20 assume you cut two penguins at once (those wing-to-wing) So the folds to get what w have on this page is 2, once in the middle, then fold that one more time to get four patterns of two penguins each.
To get 16, double that.