Over the last 1.5 years, the water level in a lake has changed by -0.5 feet per year. Scientists predict that the water level will continue to go down for the next 3 years at a rate of 0.6 feet per year. What rational number represents the overall change of the water level after 4.5 years?

a is 8.b is 10.c is 10.5. d is -.5

step-by-step explanation:

just minus the smallest number from the biggest.

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:  

on plase n