There is three different ways to find out if the figures are similar or not. Similar means when you have two figures that look the same but have different side measure. The first one is to write a ratio comparing the length of each side. You put a side from a figure as the numerator, and you choose the same side from the other figure and put it below the numerator. You will do this for a second time and if both ratios are simplified to the same number they are similar figures.
The second way is only for rectangles to find out if they are similar. You first rotate the rectangle that is not standing to a 90 degrees clockwise and it will make it look in the same position as the one standing. From here you do the same as for the first given example for finding similarity, which would be to write two ratios of the sides of the rectangles and check if they end up with the same fraction already simplified if possible.
Thirdly, this example is for photos and if they are similar to each other. You have to know the measure of the photo and multiply them by the scale factor given. A scale factor is the ratio of two corresponding sides of two similar polygons. When you have the answer from the multiplication, then you will multiply it by the measure that you want to have it. To find out if they are similar you will use the last ratios and simplify them. When they are simplified the answer will equal to the measurements of the original photo, if not it means that the photos are not similar.