What is 2000 written in scientific notation

Chandler was a caretaker at the state zoo. he noticed that the number of animals adopted by the zoo increased at a constant rate every year since 2010. which of the following graphs shows the slowest rate at which the animals in the zoo were adopted?

Maria walks a round trip of 0.75 mile to school every day. how many miles will she walk in 4.5 days

In δabc, m∠acb = 90°, cd ⊥ ab and m∠acd = 45°. find: a find cd, if bc = 3 in