Answer:
4) 0.001
Step-by-step explanation:
The amount (a) present in h hours is ...
a(h) = (initial value)×(1/2)^(h/(half-life))
6 days is 6×24 hours, so the amount remaining is ...
a(6×24) = 50×(1/2)^(6×24/9) = 50/2^16 ≈ 0.001 . . . . milligrams
a
y=1.87x+3.66
if you use a TI calculator, you can put the dots in a chart to figure this out.