Half Life Of 35 Hours A 50.0 G Sample Of (16/7) N Decays To 12.5 G In 14.4 Sec. What Is Its Half-life?

A 50.0 g sample of (16/7) N decays to 12.5 g in 14.4 sec. What is its half-life? - half life of 35 hours

I understand many aspects of life. Please send your work so that you double up the process in the future! Other questions are raised by my teacher:
The half-life (42/19) K 12.4 hours. As the 750-g sample, after 62 hours?
There are 5.0 g (131/53), I left after 40.35 days. How many grams were in the original sample, if its half-life of 8.07 days are?

Thanks to all who are in a position to help!