Mercury is a heavy metal that can cause severe health problems in even small concentrations. Fish and shellfish efficiently concentrate mercury into their flesh, so it is important to monitor seafood for its mercury content. An extensive study conducted in 1980 concluded that the mean mercury level in oysters from the White Bear estuary was 0.020 parts per million (ppm) with a standard deviation ppm. In 2012, a sample of 40 oysters from the same estuary exhibited a mean mercury concentration of . Can you conclude that the 2012 mercury concentration is lower than in 1980? Use the level of significance.

The overview of the problem is listed in the segment below on the explanation.

Step-by-step explanation:

The given values are:

Sample mean,

The hypothesized mean value,

Population standard deviation,

As we know, the status of the test is as follows:

⇒  

On putting the values, we get

⇒      

⇒      

Now, even though this is a one-sided check, here so the p-value is measured as:

Consequently p-value > 0.05 the check isn't relevant so there is no data to suggest that perhaps the concentration of mercury fallen from 1980 until 2012.  

it's d.

step-by-step explanation:

because: -1(4x + 1y) +2 (1x-3y) distribute each number into the parenthesis.

then you would get: -4x - 1y + 2x -6y combine like terms

and get: 2x -7y

hope my answer has you if not then i'm sorry.