How might scientists use inferences to learn about extinct animals from past times?

Answer 1

Looking at fossils
Carbon-dating
looking at there desendents
etc

Answer 2

Since extinct animals from the past have not been observed, excepting those "recently extinct" - dodo bird, carrier pidgeon, etc. all information promulgated by scientists is by inference. What color were the dinosaurs? No one really knows but based on living similiar type animals, scientist can infer the color. The measurement of skulls, bones, teeth, etc. all lead scientists to make inferences about how the animal fed, walked, socialized, etc. You could call their inference 'best guess'.