If i fail this class i have to do it again and this is my last chance to bring up my (questions are in the photo(s) provided) you so much in advance!

I hope this helps. Good luck, I was in the same boat not too long ago.

the answer is -1 for this question

step-by-step explanation:

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source: