The values of x, y, and z are 1, 2, and 3 respectively after using the substitution method.
<h3>What is a linear equation?</h3>
It is defined as the relation between two variables, if we plot the graph of the linear equation we will get a straight line.
If in the linear equation, one variable is present, then the equation is known as the linear equation in one variable.
We have a linear equation in three variable:
2x + 3y - z = 5 ...(1)
4x - y - z = -1 ...(2)
x + 4y + z = 12 ...(3)
(from the equation 1 and 2)
After solving:

From the above, two equations:
y =2
z =3
Plug the above values in equation 1
x = 1
Thus, the values of x, y, and z are 1, 2, and 3 respectively after using the substitution method.
Learn more about the linear equation here:
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Answer:
So
Step-by-step explanation:
Answer: 14 miles ≤ D ≤ 22 miles.
Step-by-step explanation:
The mean distance traveled per gallon, is 18 miles.
But this can fluctuate, at most, by 4 miles.
Because we have here the "at most", we know that we should use the ≤, ≥ symbols.
Then, if the mean is 18mi, the range of possible distances traveled per gallon is:
(18 miles - 4 miles) ≤ D ≤ (18 miles + 4 miles)
Where D is the distance.
14 miles ≤ D ≤ 22 miles.
So the truck can get between 14 miles and 22 miles per gallon on the highway.