Types of chemical review... please help

Must be negative.substance increases

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.

The answer is the third choice

Polyethylene is a strong synthetic polymer that can be used to make toys and bottles. this makes plastics which are important also to people but sometimes it lead to harmful environmental effects such as global warming if these plastics are burned.