Plz help me with this problem it’s not that hard at all !!

The half-life of a certain material is 0.004 second. approximately how much of a 20-gram sample will be left after 0.016 second? a. 5 grams b. 16 grams c. 0.32 gram d. 1.25 grams

If the average of x, y and z is 15 what is their sum

What is the probability of getting heads when flipping a coin and getting a number greater than or equal to 4 when rolling a single die?