How old are the oldest fossils on earth?
why do we put salt on sidewalks when it snows?
what is it that makes diseases caused by viruses and bacteria hard to treat?

5000million years are the fossils created and bacterias created

1: About 3.8 billion years; they're bacteria-like organisms.

2: Adding salt to snow or ice increases the number of molecules on the ground surface and makes it harder for the water to freeze. Salt can lower freezing temperatures on sidewalks to 15 degrees from 32 degrees.

3: Influenza viruses and others continually change over time, usually by mutation. This change enables the virus to evade the immune system of its host so that people are susceptible to influenza virus infection throughout their lives. Bacteria mutate in the same way and can also become resistant if overtreated with antibiotics

Hope it helped