Well, the angles are the same, what's the ratio of the sides? 20/16 and 11/8.8, which are equal (1.25). Yup, they're similar.

You'd have to flip it, so there's a (-) in the scale factor.

But what's the scale factor? It's basically the size ratio of one to the other. Similar sides are 20 and 11, so the scale factor is -20/11 (or -11/20, depending on which one you were starting with.)