What three types of evidence allows us to determine whether organisms shared a common ancestor?

The evidence of common ancestry is based on study of three   parameters;   fossils record, homologies of various organisms, and study of biogeography. Fossils record   determines the similarity and differences of bones as well as shells of different organisms   over a given period of time.   On the other hand, studying of homologies involves assessment of mitochondrial DNA and other proteins with an aim of finding similarity from one organism to another.  Finally, Biogeography is the assessment of how continental drift might have separated organisms which had got common ancestry and they were living together.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.