Aradioactive substance decays exponentially. a scientist begins with 120 milligrams of a radioactive substance. after 14 hours, 60 mg of the substance remains. how many milligrams will remain after 19 hours?

First thing is you have to find the half life of the substance. The half life equation is
Final Mass = Initial Mass * 0.5^(time/time per half life)
Now we substitute the values given and we get
60 mg = 120 * 0.5^(14/t)
Solve for t and you get
t = 14 hours
Now plug 19 into the equation
Final Mass = 120 * 0.5^(19/14)
Final Mass = 46.84 mg