Kevin calculated the product of 3.2 × 104 and 3.6 × 102 as 11.52 × 106. Which is the next step that Kevin should apply to his solution?

yes.. it's proven to be 36.

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:  

what is the question you are asking?