If 80% of a radioactive element remains radioactive after 300 million years, then what percent remains radioactive after 700 million years? What is the half-life of this element? What percent remains radioactive after 700 million years? % (Do not round until the final answer. Then round to the nearest integer as needed.)

Answer? preferably with an explanation

C For all of the remaining questions, show or describe your work. 3. The mass of a sample of a mystery element is measured periodically as it decays. If 0.78 % of the sample remains after 100 days, what is the half-life of the element?

Seaborgium-266 is a radioactive metal that does not occur naturally and only a few atoms have ever been made. a) How many protons does Seaborgium have? b). How many neutrons does Seaborgium have Seaborgium-266 has a half-life of 30 seconds. If there are initially 30 grams in a sample of seaborgium-266. c) How long will it take to decay to 7.5 g? d To the nearest hundredth of a gram how much of the original remains after three minutes have elapsed?