Here you have to find which each variable is, for this you start of picking one equation,
x + 2y + 6z = 4
-3x + 2y - 2 = -4
4x + 2z = 16
depending the equation you pick you multiply that by a certain number that will give you the opposite of one of the other equations,
-1(x + 2y + 6z = 4)
= -x -2y - 6z = -4
With this you add or subtract it with the equation that has the same number or variable, or both,
In this case it will be the equation,
-3x + 2y + 6z = 4
You can use this one or the third equation since both have a positive 2y which will cancel with -2y from the new equation,
-x - 2y - 6z = -4
-3x + 2y -z = -4
= -4x -7z = -8
Now you since you just eliminated the variable (y) you now have 2 variables, and the last equation has only 2 variables, meaning now you find the answer to those to equations,
-4x -7z = -8
4x + 2z = 16
= -5z = 8
Now leave the variable by itself,
z = 8/5
Now you found the variable (z), with this just substitute on one of the equations we used to find (z) so you can find (x), after that substitute those answered to on of the original equations so you can find (y)
This would just be 7 1/5 + 3/5 since the negative sign gets distributed and makes (-3/5) into a positive number.
From there you have basic math and you get 7 4/5.
By looking at the graph you can rule out choices C and D because the graph given to you is an increasing linear function and C and D represent functions with a decreasing or negative slope.
By looking at the picture the slop of the graph seems to be 4/1 (rise/run) so your slope is 4. And your y-intercept looks like its -4 so your answer is B<span />
Check the picture.
let the length of a side of each of the squares removed be x.
The box formed will have dimensions: 80-2x, 50-2x, x(the height)
So the volume can be expressed as a function of x as follows:
f(x)=(80-2x)(50-2x)x=
![[4000-160x-100x+4 x^{2} ]x=(4 x^{2}-260x+4000)x](https://tex.z-dn.net/?f=%5B4000-160x-100x%2B4%20x%5E%7B2%7D%20%5Dx%3D%284%20x%5E%7B2%7D-260x%2B4000%29x)
so

the solutions of f'(x)=0 gives the inflection points, so the candidates for maxima points,

solving the quadratic equation, either by a calculator, graphing software, or by other algebraic methods as the discriminant formula, we find the solutions
x=10 and x=33.333
plug in f(x) these values to see which greater:

cm cubed

which is negative because (50-66.666)<0
Answer: 18000 cm cubed