Can any number be written in scientific notation

1. what are the missing reasons in the proof 2. it's in the second picture and 3

Toyland is having a sale. all items are 20% off. how much will you save on an item that usually sells for 95$ explain your

According to modern science, earth is about 4.5 billion years old and written human history extends back about 10,000 years. suppose the entire history of earth is represented with a 10-meter-long timeline, with the birth of earth on one end and today at the other end.