What operation should be performed first in the expression 8 - 2 + 5 x (16 + 66 didved by 2)

8 - 2 + 5 x ( 16 + 66 ÷ 2)

Do the ÷ in the bracket:

= 8 - 2 + 5 x ( 16 + 33)

Do the operation in the bracket:

= 8 - 2 + 5 x 49

Do multiplication:

= 8 - 2 + 245

Do subtraction:

= 6 + 245

Do addition:

= 251

-

251

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:  

x:       y:  

-1         4

0         4

1         6

2         18

3         20