I don’t know how to do it

i dont know and i dont care for math bc it is a stupied subject

step-by-step explanation:

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225

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: