Ginitially 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.) -g

See attached graphic, formula #2
y(t) = a * e^k*t
y(t) - ending amount
a - beginning amount
k - rate
t - time
e - 2.718281828459

We first must solve for "k"

k = [ln[y(t) / a]] / t
k = [ln [96 mg / 100 mg]] / 6
k = ln (.96) / 6
k = -.04082199452 / 6
k = -0.0068036658

y(t) = 100 mg * 2.71828^ ( -0.0068036658 *24)
y(t) = 100 mg * 2.71828^ -0.1632879792
y(t) = 100 mg * 0.8493466523
y(t) = 84.9 milligrams

Source:
http://1728.org/expgrwt2.htm

If you make you answer for clear i can answer it : )