Please, please, please helppp

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.)

What are the solutions to the following equation? |m| = 8.5 the value of m is equal to 8.5 and because each distance from zero is 8.5.

Could somebody me with this radical simplification?