Please help me ill mark you as brainiset

Write a polynomial for a third-degree polynomial with leading coefficient -4

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.)

Translate the word phrase into a math expression. 15 fewer than the product of 4 and a number. (pls immediately)