Adrian currently has $400 in his savings account. He saves $20 per month. He saves the same amount each month and does not take any money out of the account. In how many months will Adrian have $700 in his savings account?
O 35 months
o 15 months
o 55 months
o 20 months

15

Step-by-step explanation:

if 5 20s is 100 then do it times three if that makes sence lol

12

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: