Hello!
Let’s start with the definition of “similar” figures (this definition is from varsity tutors):
Two figures are said to be similar if they are the same shape. In more mathematical language, two figures are similar if their corresponding angles are congruent , and the ratios of the lengths of their corresponding sides are equal.
Therefore, we know that the sides of the smaller figure will be at an equal ratio to the sides of the larger figure.
The smaller figure is flipped upside down as opposed to the larger one. Therefore, the bottom (8) of the small figure has a ratio with top (12) of the large figure.
The resulting ratio is 8:12
You can simplify that! Divide both 8 and 12 by 4.
8/4=2
12/4= 3
Therefore, your final ratio is 2:3!
Hope this helped. Comment if you have questions!