Help please, this is a practice test for my state test and im confused

Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)

Could someone with number 1 and 2

What is the value of f(x) = 2.2 for f(-2)?