Look at the problem below im taking a test need answer fast I am struggling

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.)

Evaluate-27 ^4/3/8 a) - 81/16 b) 81/16 c) 16/81

Simplify the expression below -3(10x+4y)+6(6x-2y)