Answer:i believe the answer is -54
Hope this helped!
Step-by-step explanation:
First you wanna distribute the 3 to x and 4
So the problem will then be 3x+12= 27
Then you wanna subtract 12 from 27
You get 3x = 15
Now you wanna divide 3x and 15 by 3
You then get X = 5
(N instead of X for variable)
N x 7 < 21
Answer: Approximately 1.9 atm
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Work Shown:

If the volume is 3.5 liters, then the pressure is approximately 1.9 atm.
Note the increase in volume leads to the reduction of pressure, and vice versa. The two variables have an inverse relationship.
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As a check,

We don't get the exact thing on both sides, but the two sides are close enough. We have rounding error due to P2 being not exact.
A more accurate check could be

which has the two sides much closer to one another. This helps us verify the answer.
25(0.2)+25 multiply 25 by 0.2 to find 20% of $25 then add that to the bill of $25