Answer:
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Step-by-step explanation:
The difference in gallons per day used is 3.6.
The formula to calculate a z-score is:

,
where X is the value used to calculate the score, μ is the mean and σ is the standard deviation. We have the z-scores so we must work backward:

For both equations, we will cancel the 1.2 by multiplying both sides:

Now we will cancel 2.2 from both equations by adding it to both sides:
3.6+2.2=X-2.2+2.2 and 0+2.2=X-2.2+2.2
5.8=X and 2.2=X
The difference in gas used per day would be given by
5.8-2.2 = 3.6.
I don’t see the image can you please add one to the comments so I can answer it. Thanks
In order to solve this problem, we must solve an equation.
First, we need to define our unknown.
Let's call our number "n".
So, the sum of the number and 6 is the same as saying n+6
Then we need to multiply it by 2 (since it's twice the sum)
2(n+6)
This whole thing is equal to three times of the difference of the number and 8
n-8 is equal to the difference between the number and 8, then we need to multiply it by three.
3(n-8)
now, we set both sides equal and solve

The number is 36