Which equation has the solution of x=9

I'm so close to finishing all these.

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.)

Pj is decorating pupcakes for rocky's birthday party. her color scheme is black, purple, and green. she will use this spinner to determine the color of sprinkles on each pupcake. which model shows the probability of randomly landing on each color?