Studying the anatomy of different organisms allows scientists to determine how different species have evolved over time.

An eagle. A butterfly.

Which type of anatomic structure are bird wings and butterfly wings when compared to each other?
vestigial
homologous
analogous
heterologous

The correct answer is analogous.

Explanation:

The organs, which have lost their ancestral function with time or with evolution are known as the vestigial organs. The organs that are found in distinct species and exhibit identical activity, however, distinct origin are known as analogous organs.  

The organs that neither possess identical function nor do they exhibit the similar origin are known as the heterologous organs. While the organs found in different organisms that possess distinct functions, but are similar in origin are known as the homologous organs. Therefore, it can be stated that the wings of the birds like eagle and wings of the butterfly are the examples of analogous organs as they are distinct in origin, but possess identical function.  

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)