An element with mass 780 grams decays by 16.3% per minute. how much of the element is remaining after 16 minutes, to the nearest 10th of a gram?

Exponential decay is a very common process especially when we are talking about radioactive materials. So, there is already a common formula for this type of behavior which is written below:

A = Pe^-rt
where
A is the amount left after time t
P is the initial amount at t=0
r is the rate

Substituting the values,
A = (780 g)(e^-0.163*16)
A = 57.5 g

The answer should be c.